[PATCH v3 00/13] SMM emulation and interrupt shadow fixes

[PATCH v3 00/13] SMM emulation and interrupt shadow fixes

[Maxim Levitsky]

This patch series is a result of long debug work to find out why
sometimes guests with win11 secure boot
were failing during boot.

During writing a unit test I found another bug, turns out
that on rsm emulation, if the rsm instruction was done in real
or 32 bit mode, KVM would truncate the restored RIP to 32 bit.

I also refactored the way we write SMRAM so it is easier
now to understand what is going on.

The main bug in this series which I fixed is that we
allowed #SMI to happen during the STI interrupt shadow,
and we did nothing to both reset it on #SMI handler
entry and restore it on RSM.

V3: addressed most of the review feedback from Sean (thanks!)

Best regards,
	Maxim Levitsky

Maxim Levitsky (13):
  bug: introduce ASSERT_STRUCT_OFFSET
  KVM: x86: emulator: em_sysexit should update ctxt->mode
  KVM: x86: emulator: introduce emulator_recalc_and_set_mode
  KVM: x86: emulator: update the emulation mode after rsm
  KVM: x86: emulator: update the emulation mode after CR0 write
  KVM: x86: emulator/smm: number of GPRs in the SMRAM image depends on
    the image format
  KVM: x86: emulator/smm: add structs for KVM's smram layout
  KVM: x86: emulator/smm: use smram structs in the common code
  KVM: x86: emulator/smm: use smram struct for 32 bit smram load/restore
  KVM: x86: emulator/smm: use smram struct for 64 bit smram load/restore
  KVM: x86: SVM: use smram structs
  KVM: x86: SVM: don't save SVM state to SMRAM when VM is not long mode
    capable
  KVM: x86: emulator/smm: preserve interrupt shadow in SMRAM

 arch/x86/include/asm/kvm_host.h |  11 +-
 arch/x86/kvm/emulate.c          | 305 +++++++++++++++++---------------
 arch/x86/kvm/kvm_emulate.h      | 223 ++++++++++++++++++++++-
 arch/x86/kvm/svm/svm.c          |  30 ++--
 arch/x86/kvm/vmx/vmcs12.h       |   5 +-
 arch/x86/kvm/vmx/vmx.c          |   4 +-
 arch/x86/kvm/x86.c              | 175 +++++++++---------
 include/linux/build_bug.h       |   9 +
 8 files changed, 497 insertions(+), 265 deletions(-)

-- 
2.26.3

[PATCH v3 01/13] bug: introduce ASSERT_STRUCT_OFFSET

[Maxim Levitsky]

ASSERT_STRUCT_OFFSET allows to assert during the build of
the kernel that a field in a struct have an expected offset.

KVM used to have such macro, but there is almost nothing KVM specific
in it so move it to build_bug.h, so that it can be used in other
places in KVM.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 arch/x86/kvm/vmx/vmcs12.h | 5 ++---
 include/linux/build_bug.h | 9 +++++++++
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmcs12.h b/arch/x86/kvm/vmx/vmcs12.h
index 746129ddd5ae02..01936013428b5c 100644
--- a/arch/x86/kvm/vmx/vmcs12.h
+++ b/arch/x86/kvm/vmx/vmcs12.h
@@ -208,9 +208,8 @@ struct __packed vmcs12 {
 /*
  * For save/restore compatibility, the vmcs12 field offsets must not change.
  */
-#define CHECK_OFFSET(field, loc)				\
-	BUILD_BUG_ON_MSG(offsetof(struct vmcs12, field) != (loc),	\
-		"Offset of " #field " in struct vmcs12 has changed.")
+#define CHECK_OFFSET(field, loc) \
+	ASSERT_STRUCT_OFFSET(struct vmcs12, field, loc)
 
 static inline void vmx_check_vmcs12_offsets(void)
 {
diff --git a/include/linux/build_bug.h b/include/linux/build_bug.h
index e3a0be2c90ad98..3aa3640f8c181f 100644
--- a/include/linux/build_bug.h
+++ b/include/linux/build_bug.h
@@ -77,4 +77,13 @@
 #define static_assert(expr, ...) __static_assert(expr, ##__VA_ARGS__, #expr)
 #define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
 
+
+/*
+ * Compile time check that field has an expected offset
+ */
+#define ASSERT_STRUCT_OFFSET(type, field, expected_offset)	\
+	BUILD_BUG_ON_MSG(offsetof(type, field) != (expected_offset),	\
+		"Offset of " #field " in " #type " has changed.")
+
+
 #endif	/* _LINUX_BUILD_BUG_H */
-- 
2.26.3

[PATCH v3 02/13] KVM: x86: emulator: em_sysexit should update ctxt->mode

[Maxim Levitsky]

This is one of the instructions that can change the
processor mode.

Note that this is likely a benign bug, because the only problematic
mode change is from 32 bit to 64 bit which can lead to truncation of RIP,
and it is not possible to do with sysexit,
since sysexit running in 32 bit mode will be limited to 32 bit version.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 arch/x86/kvm/emulate.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 047c583596bb86..7bdc495710bd0e 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2888,6 +2888,7 @@ static int em_sysexit(struct x86_emulate_ctxt *ctxt)
 	ops->set_segment(ctxt, ss_sel, &ss, 0, VCPU_SREG_SS);
 
 	ctxt->_eip = rdx;
+	ctxt->mode = usermode;
 	*reg_write(ctxt, VCPU_REGS_RSP) = rcx;
 
 	return X86EMUL_CONTINUE;
-- 
2.26.3

[PATCH v3 03/13] KVM: x86: emulator: introduce emulator_recalc_and_set_mode

[Maxim Levitsky]

Some instructions update the cpu execution mode, which needs
to update the emulation mode.

Extract this code, and make assign_eip_far use it.

assign_eip_far now reads CS, instead of getting it via a parameter,
which is ok, because callers always assign CS to the
same value before calling it.

No functional change is intended.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 arch/x86/kvm/emulate.c | 85 ++++++++++++++++++++++++++++--------------
 1 file changed, 57 insertions(+), 28 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 7bdc495710bd0e..bc70caf403c2b4 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -805,8 +805,7 @@ static int linearize(struct x86_emulate_ctxt *ctxt,
 			   ctxt->mode, linear);
 }
 
-static inline int assign_eip(struct x86_emulate_ctxt *ctxt, ulong dst,
-			     enum x86emul_mode mode)
+static inline int assign_eip(struct x86_emulate_ctxt *ctxt, ulong dst)
 {
 	ulong linear;
 	int rc;
@@ -816,41 +815,71 @@ static inline int assign_eip(struct x86_emulate_ctxt *ctxt, ulong dst,
 
 	if (ctxt->op_bytes != sizeof(unsigned long))
 		addr.ea = dst & ((1UL << (ctxt->op_bytes << 3)) - 1);
-	rc = __linearize(ctxt, addr, &max_size, 1, false, true, mode, &linear);
+	rc = __linearize(ctxt, addr, &max_size, 1, false, true, ctxt->mode, &linear);
 	if (rc == X86EMUL_CONTINUE)
 		ctxt->_eip = addr.ea;
 	return rc;
 }
 
+static inline int emulator_recalc_and_set_mode(struct x86_emulate_ctxt *ctxt)
+{
+	u64 efer;
+	struct desc_struct cs;
+	u16 selector;
+	u32 base3;
+
+	ctxt->ops->get_msr(ctxt, MSR_EFER, &efer);
+
+	if (!ctxt->ops->get_cr(ctxt, 0) & X86_CR0_PE) {
+		/* Real mode. cpu must not have long mode active */
+		if (efer & EFER_LMA)
+			return X86EMUL_UNHANDLEABLE;
+		ctxt->mode = X86EMUL_MODE_REAL;
+		return X86EMUL_CONTINUE;
+	}
+
+	if (ctxt->eflags & X86_EFLAGS_VM) {
+		/* Protected/VM86 mode. cpu must not have long mode active */
+		if (efer & EFER_LMA)
+			return X86EMUL_UNHANDLEABLE;
+		ctxt->mode = X86EMUL_MODE_VM86;
+		return X86EMUL_CONTINUE;
+	}
+
+	if (!ctxt->ops->get_segment(ctxt, &selector, &cs, &base3, VCPU_SREG_CS))
+		return X86EMUL_UNHANDLEABLE;
+
+	if (efer & EFER_LMA) {
+		if (cs.l) {
+			/* Proper long mode */
+			ctxt->mode = X86EMUL_MODE_PROT64;
+		} else if (cs.d) {
+			/* 32 bit compatibility mode*/
+			ctxt->mode = X86EMUL_MODE_PROT32;
+		} else {
+			ctxt->mode = X86EMUL_MODE_PROT16;
+		}
+	} else {
+		/* Legacy 32 bit / 16 bit mode */
+		ctxt->mode = cs.d ? X86EMUL_MODE_PROT32 : X86EMUL_MODE_PROT16;
+	}
+
+	return X86EMUL_CONTINUE;
+}
+
 static inline int assign_eip_near(struct x86_emulate_ctxt *ctxt, ulong dst)
 {
-	return assign_eip(ctxt, dst, ctxt->mode);
+	return assign_eip(ctxt, dst);
 }
 
-static int assign_eip_far(struct x86_emulate_ctxt *ctxt, ulong dst,
-			  const struct desc_struct *cs_desc)
+static int assign_eip_far(struct x86_emulate_ctxt *ctxt, ulong dst)
 {
-	enum x86emul_mode mode = ctxt->mode;
-	int rc;
+	int rc = emulator_recalc_and_set_mode(ctxt);
 
-#ifdef CONFIG_X86_64
-	if (ctxt->mode >= X86EMUL_MODE_PROT16) {
-		if (cs_desc->l) {
-			u64 efer = 0;
+	if (rc != X86EMUL_CONTINUE)
+		return rc;
 
-			ctxt->ops->get_msr(ctxt, MSR_EFER, &efer);
-			if (efer & EFER_LMA)
-				mode = X86EMUL_MODE_PROT64;
-		} else
-			mode = X86EMUL_MODE_PROT32; /* temporary value */
-	}
-#endif
-	if (mode == X86EMUL_MODE_PROT16 || mode == X86EMUL_MODE_PROT32)
-		mode = cs_desc->d ? X86EMUL_MODE_PROT32 : X86EMUL_MODE_PROT16;
-	rc = assign_eip(ctxt, dst, mode);
-	if (rc == X86EMUL_CONTINUE)
-		ctxt->mode = mode;
-	return rc;
+	return assign_eip(ctxt, dst);
 }
 
 static inline int jmp_rel(struct x86_emulate_ctxt *ctxt, int rel)
@@ -2184,7 +2213,7 @@ static int em_jmp_far(struct x86_emulate_ctxt *ctxt)
 	if (rc != X86EMUL_CONTINUE)
 		return rc;
 
-	rc = assign_eip_far(ctxt, ctxt->src.val, &new_desc);
+	rc = assign_eip_far(ctxt, ctxt->src.val);
 	/* Error handling is not implemented. */
 	if (rc != X86EMUL_CONTINUE)
 		return X86EMUL_UNHANDLEABLE;
@@ -2262,7 +2291,7 @@ static int em_ret_far(struct x86_emulate_ctxt *ctxt)
 				       &new_desc);
 	if (rc != X86EMUL_CONTINUE)
 		return rc;
-	rc = assign_eip_far(ctxt, eip, &new_desc);
+	rc = assign_eip_far(ctxt, eip);
 	/* Error handling is not implemented. */
 	if (rc != X86EMUL_CONTINUE)
 		return X86EMUL_UNHANDLEABLE;
@@ -3482,7 +3511,7 @@ static int em_call_far(struct x86_emulate_ctxt *ctxt)
 	if (rc != X86EMUL_CONTINUE)
 		return rc;
 
-	rc = assign_eip_far(ctxt, ctxt->src.val, &new_desc);
+	rc = assign_eip_far(ctxt, ctxt->src.val);
 	if (rc != X86EMUL_CONTINUE)
 		goto fail;
 
-- 
2.26.3

Re: [PATCH v3 03/13] KVM: x86: emulator: introduce emulator_recalc_and_set_mode

[Yang, Weijiang]

On 8/3/2022 11:50 PM, Maxim Levitsky wrote:
> [...]
> +static inline int emulator_recalc_and_set_mode(struct x86_emulate_ctxt *ctxt)
> +{
> +       u64 efer;
> +       struct desc_struct cs;
> +       u16 selector;
> +       u32 base3;
> +
> +       ctxt->ops->get_msr(ctxt, MSR_EFER, &efer);
> +
> +       if (!ctxt->ops->get_cr(ctxt, 0) & X86_CR0_PE) {
Shouldn't this be:  !(ctxt->ops->get_cr(ctxt, 0) & X86_CR0_PE) ?
> +               /* Real mode. cpu must not have long mode active */
> +               if (efer & EFER_LMA)
> +                       return X86EMUL_UNHANDLEABLE;
> +               ctxt->mode = X86EMUL_MODE_REAL;
> +               return X86EMUL_CONTINUE;
> +       }
> +
[...]
> --
> 2.26.3
>

Re: [PATCH v3 03/13] KVM: x86: emulator: introduce emulator_recalc_and_set_mode

[Maxim Levitsky]

On Thu, 2022-08-11 at 23:33 +0800, Yang, Weijiang wrote:
> On 8/3/2022 11:50 PM, Maxim Levitsky wrote:
> > [...]
> > +static inline int emulator_recalc_and_set_mode(struct x86_emulate_ctxt *ctxt)
> > +{
> > +       u64 efer;
> > +       struct desc_struct cs;
> > +       u16 selector;
> > +       u32 base3;
> > +
> > +       ctxt->ops->get_msr(ctxt, MSR_EFER, &efer);
> > +
> > +       if (!ctxt->ops->get_cr(ctxt, 0) & X86_CR0_PE) {

Ouch, thanks for catching this!!

I wonder how I didn't catch this in unit tests....
(I'll check on this Sunday)


Best regards,
	Maxim Levitsky

> Shouldn't this be:  !(ctxt->ops->get_cr(ctxt, 0) & X86_CR0_PE) ?
> > +               /* Real mode. cpu must not have long mode active */
> > +               if (efer & EFER_LMA)
> > +                       return X86EMUL_UNHANDLEABLE;
> > +               ctxt->mode = X86EMUL_MODE_REAL;
> > +               return X86EMUL_CONTINUE;
> > +       }
> > +
> [...]
> > --
> > 2.26.3
> > 

Re: [PATCH v3 03/13] KVM: x86: emulator: introduce emulator_recalc_and_set_mode

[Maxim Levitsky]

On Thu, 2022-08-11 at 23:33 +0800, Yang, Weijiang wrote:
> 
> On 8/3/2022 11:50 PM, Maxim Levitsky wrote:
> > [...]
> > +static inline int emulator_recalc_and_set_mode(struct x86_emulate_ctxt *ctxt)
> > +{
> > +       u64 efer;
> > +       struct desc_struct cs;
> > +       u16 selector;
> > +       u32 base3;
> > +
> > +       ctxt->ops->get_msr(ctxt, MSR_EFER, &efer);
> > +
> > +       if (!ctxt->ops->get_cr(ctxt, 0) & X86_CR0_PE) {
> Shouldn't this be:  !(ctxt->ops->get_cr(ctxt, 0) & X86_CR0_PE) ?

Ouch, thanks for noticing this!
I'll fix it in v4 (I'll wait a bit if I get more review feedback before sending it).

Best regards,
	Maxim Levitsky




> > +               /* Real mode. cpu must not have long mode active */
> > +               if (efer & EFER_LMA)
> > +                       return X86EMUL_UNHANDLEABLE;
> > +               ctxt->mode = X86EMUL_MODE_REAL;
> > +               return X86EMUL_CONTINUE;
> > +       }
> > +
> [...]
> > --
> > 2.26.3
> > 
> 

[PATCH v3 04/13] KVM: x86: emulator: update the emulation mode after rsm

[Maxim Levitsky]

This ensures that RIP will be correctly written back,
because the RSM instruction can switch the CPU mode from
32 bit (or less) to 64 bit.

This fixes a guest crash in case the #SMI is received
while the guest runs a code from an address > 32 bit.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 arch/x86/kvm/emulate.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index bc70caf403c2b4..5e91b26cc1d8aa 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2666,6 +2666,11 @@ static int em_rsm(struct x86_emulate_ctxt *ctxt)
 	if (ret != X86EMUL_CONTINUE)
 		goto emulate_shutdown;
 
+
+	ret = emulator_recalc_and_set_mode(ctxt);
+	if (ret != X86EMUL_CONTINUE)
+		goto emulate_shutdown;
+
 	/*
 	 * Note, the ctxt->ops callbacks are responsible for handling side
 	 * effects when writing MSRs and CRs, e.g. MMU context resets, CPUID
-- 
2.26.3

Re: [PATCH v3 04/13] KVM: x86: emulator: update the emulation mode after rsm

[Sean Christopherson]

On Wed, Aug 03, 2022, Maxim Levitsky wrote:

Please make the changelog standalone, even though it means restating the shortlog
in most cases.  When viewing git commits, the shortlog+changelog are bundled
fairly close together, but when viewing patches in a mail client, e.g. when doing
initial review, the shortlog is in the subject which may be far away or even
completely hidden.

> This ensures that RIP will be correctly written back,
> because the RSM instruction can switch the CPU mode from
> 32 bit (or less) to 64 bit.

Wrap closer to ~75 chars.

> 
> This fixes a guest crash in case the #SMI is received
> while the guest runs a code from an address > 32 bit.
> 
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> ---
>  arch/x86/kvm/emulate.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index bc70caf403c2b4..5e91b26cc1d8aa 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -2666,6 +2666,11 @@ static int em_rsm(struct x86_emulate_ctxt *ctxt)
>  	if (ret != X86EMUL_CONTINUE)
>  		goto emulate_shutdown;
>  
> +

Unnecessary newline.

> +	ret = emulator_recalc_and_set_mode(ctxt);
> +	if (ret != X86EMUL_CONTINUE)
> +		goto emulate_shutdown;
> +
>  	/*
>  	 * Note, the ctxt->ops callbacks are responsible for handling side
>  	 * effects when writing MSRs and CRs, e.g. MMU context resets, CPUID
> -- 
> 2.26.3
> 

[PATCH v3 05/13] KVM: x86: emulator: update the emulation mode after CR0 write

[Maxim Levitsky]

CR0.PE toggles real/protected mode, thus its update
should update the emulation mode.

This is likely a benign bug because there is no writeback
of state, other than the RIP increment, and when toggling
CR0.PE, the CPU has to execute code from a very low memory address.

Also CR0.PG toggle when EFER.LMA is set, toggles the long mode.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 arch/x86/kvm/emulate.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 5e91b26cc1d8aa..765ec65b2861ba 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3658,11 +3658,23 @@ static int em_movbe(struct x86_emulate_ctxt *ctxt)
 
 static int em_cr_write(struct x86_emulate_ctxt *ctxt)
 {
-	if (ctxt->ops->set_cr(ctxt, ctxt->modrm_reg, ctxt->src.val))
+	int cr_num = ctxt->modrm_reg;
+	int r;
+
+	if (ctxt->ops->set_cr(ctxt, cr_num, ctxt->src.val))
 		return emulate_gp(ctxt, 0);
 
 	/* Disable writeback. */
 	ctxt->dst.type = OP_NONE;
+
+	if (cr_num == 0) {
+		/* CR0 write might have updated CR0.PE and/or CR0.PG
+		 * which can affect the cpu execution mode */
+		r = emulator_recalc_and_set_mode(ctxt);
+		if (r != X86EMUL_CONTINUE)
+			return r;
+	}
+
 	return X86EMUL_CONTINUE;
 }
 
-- 
2.26.3

Re: [PATCH v3 05/13] KVM: x86: emulator: update the emulation mode after CR0 write

[Sean Christopherson]

On Wed, Aug 03, 2022, Maxim Levitsky wrote:
> CR0.PE toggles real/protected mode, thus its update

Uber nit, I like using title case for Real Mode, Protected Mode, etc... so that
it's more obvious that a changelog/comment is referring to the architectural modes.

> should update the emulation mode.
> 
> This is likely a benign bug because there is no writeback
> of state, other than the RIP increment, and when toggling
> CR0.PE, the CPU has to execute code from a very low memory address.
> 
> Also CR0.PG toggle when EFER.LMA is set, toggles the long mode.

This last sentence is jumbled, and it probably fits better with the opening
sentence.  And it's technically EFER.LME; EFER.LMA=1 indicates the Long Mode is
fully active.  E.g. something like

  Update the emulation mode when handling writes to CR0, toggling CR0.PE switches
  between Real and Protected Mode, and toggling CR0.PG when EFER.LME=1 switches
  between Long and Protected Mode.

> 
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> ---
>  arch/x86/kvm/emulate.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index 5e91b26cc1d8aa..765ec65b2861ba 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -3658,11 +3658,23 @@ static int em_movbe(struct x86_emulate_ctxt *ctxt)
>  
>  static int em_cr_write(struct x86_emulate_ctxt *ctxt)
>  {
> -	if (ctxt->ops->set_cr(ctxt, ctxt->modrm_reg, ctxt->src.val))
> +	int cr_num = ctxt->modrm_reg;
> +	int r;
> +
> +	if (ctxt->ops->set_cr(ctxt, cr_num, ctxt->src.val))
>  		return emulate_gp(ctxt, 0);
>  
>  	/* Disable writeback. */
>  	ctxt->dst.type = OP_NONE;
> +
> +	if (cr_num == 0) {
> +		/* CR0 write might have updated CR0.PE and/or CR0.PG
> +		 * which can affect the cpu execution mode */

		/*
		 * Multi-line comment format should look like this.  I need more
		 * words to make this multiple lines.
		 */

> +		r = emulator_recalc_and_set_mode(ctxt);
> +		if (r != X86EMUL_CONTINUE)
> +			return r;
> +	}
> +
>  	return X86EMUL_CONTINUE;
>  }
>  
> -- 
> 2.26.3
> 

[PATCH v3 06/13] KVM: x86: emulator/smm: number of GPRs in the SMRAM image depends on the image format

[Maxim Levitsky]

On 64 bit host, if the guest doesn't have X86_FEATURE_LM, KVM will
access 16 gprs to 32-bit smram image, causing out-ouf-bound ram
access.

On 32 bit host, the rsm_load_state_64/enter_smm_save_state_64
is compiled out, thus access overflow can't happen.

Fixes: b443183a25ab61 ("KVM: x86: Reduce the number of emulator GPRs to '8' for 32-bit KVM")

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/emulate.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 765ec65b2861ba..18551611cb13af 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2473,7 +2473,7 @@ static int rsm_load_state_32(struct x86_emulate_ctxt *ctxt,
 	ctxt->eflags =             GET_SMSTATE(u32, smstate, 0x7ff4) | X86_EFLAGS_FIXED;
 	ctxt->_eip =               GET_SMSTATE(u32, smstate, 0x7ff0);
 
-	for (i = 0; i < NR_EMULATOR_GPRS; i++)
+	for (i = 0; i < 8; i++)
 		*reg_write(ctxt, i) = GET_SMSTATE(u32, smstate, 0x7fd0 + i * 4);
 
 	val = GET_SMSTATE(u32, smstate, 0x7fcc);
@@ -2530,7 +2530,7 @@ static int rsm_load_state_64(struct x86_emulate_ctxt *ctxt,
 	u16 selector;
 	int i, r;
 
-	for (i = 0; i < NR_EMULATOR_GPRS; i++)
+	for (i = 0; i < 16; i++)
 		*reg_write(ctxt, i) = GET_SMSTATE(u64, smstate, 0x7ff8 - i * 8);
 
 	ctxt->_eip   = GET_SMSTATE(u64, smstate, 0x7f78);
-- 
2.26.3

[PATCH v3 07/13] KVM: x86: emulator/smm: add structs for KVM's smram layout

[Maxim Levitsky]

Those structs will be used to read/write the smram state image.

Also document the differences between KVM's SMRAM layout and SMRAM
layout that is used by real Intel/AMD cpus.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 arch/x86/kvm/emulate.c     |   6 +
 arch/x86/kvm/kvm_emulate.h | 218 +++++++++++++++++++++++++++++++++++++
 arch/x86/kvm/x86.c         |   1 +
 3 files changed, 225 insertions(+)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 18551611cb13af..55d9328e6074a2 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -5864,3 +5864,9 @@ bool emulator_can_use_gpa(struct x86_emulate_ctxt *ctxt)
 
 	return true;
 }
+
+void  __init kvm_emulator_init(void)
+{
+	__check_smram32_offsets();
+	__check_smram64_offsets();
+}
diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
index 89246446d6aa9d..dd0ae61e44a116 100644
--- a/arch/x86/kvm/kvm_emulate.h
+++ b/arch/x86/kvm/kvm_emulate.h
@@ -13,6 +13,7 @@
 #define _ASM_X86_KVM_X86_EMULATE_H
 
 #include <asm/desc_defs.h>
+#include <linux/build_bug.h>
 #include "fpu.h"
 
 struct x86_emulate_ctxt;
@@ -503,6 +504,223 @@ enum x86_intercept {
 	nr_x86_intercepts
 };
 
+
+/* 32 bit KVM's emulated SMM layout. Loosely based on Intel's layout */
+
+struct kvm_smm_seg_state_32 {
+	u32 flags;
+	u32 limit;
+	u32 base;
+} __packed;
+
+struct kvm_smram_state_32 {
+	u32 reserved1[62];
+	u32 smbase;
+	u32 smm_revision;
+	u32 reserved2[5];
+	u32 cr4; /* CR4 is not present in Intel/AMD SMRAM image */
+	u32 reserved3[5];
+
+	/*
+	 * Segment state is not present/documented in the Intel/AMD SMRAM image
+	 * Instead this area on Intel/AMD contains IO/HLT restart flags.
+	 */
+	struct kvm_smm_seg_state_32 ds;
+	struct kvm_smm_seg_state_32 fs;
+	struct kvm_smm_seg_state_32 gs;
+	struct kvm_smm_seg_state_32 idtr; /* IDTR has only base and limit */
+	struct kvm_smm_seg_state_32 tr;
+	u32 reserved;
+	struct kvm_smm_seg_state_32 gdtr; /* GDTR has only base and limit */
+	struct kvm_smm_seg_state_32 ldtr;
+	struct kvm_smm_seg_state_32 es;
+	struct kvm_smm_seg_state_32 cs;
+	struct kvm_smm_seg_state_32 ss;
+
+	u32 es_sel;
+	u32 cs_sel;
+	u32 ss_sel;
+	u32 ds_sel;
+	u32 fs_sel;
+	u32 gs_sel;
+	u32 ldtr_sel;
+	u32 tr_sel;
+
+	u32 dr7;
+	u32 dr6;
+	u32 gprs[8]; /* GPRS in the "natural" X86 order (EAX/ECX/EDX.../EDI) */
+	u32 eip;
+	u32 eflags;
+	u32 cr3;
+	u32 cr0;
+} __packed;
+
+
+static inline void __check_smram32_offsets(void)
+{
+#define __CHECK_SMRAM32_OFFSET(field, offset) \
+	ASSERT_STRUCT_OFFSET(struct kvm_smram_state_32, field, offset - 0xFE00)
+
+	__CHECK_SMRAM32_OFFSET(reserved1,	0xFE00);
+	__CHECK_SMRAM32_OFFSET(smbase,		0xFEF8);
+	__CHECK_SMRAM32_OFFSET(smm_revision,	0xFEFC);
+	__CHECK_SMRAM32_OFFSET(reserved2,	0xFF00);
+	__CHECK_SMRAM32_OFFSET(cr4,		0xFF14);
+	__CHECK_SMRAM32_OFFSET(reserved3,	0xFF18);
+	__CHECK_SMRAM32_OFFSET(ds,		0xFF2C);
+	__CHECK_SMRAM32_OFFSET(fs,		0xFF38);
+	__CHECK_SMRAM32_OFFSET(gs,		0xFF44);
+	__CHECK_SMRAM32_OFFSET(idtr,		0xFF50);
+	__CHECK_SMRAM32_OFFSET(tr,		0xFF5C);
+	__CHECK_SMRAM32_OFFSET(gdtr,		0xFF6C);
+	__CHECK_SMRAM32_OFFSET(ldtr,		0xFF78);
+	__CHECK_SMRAM32_OFFSET(es,		0xFF84);
+	__CHECK_SMRAM32_OFFSET(cs,		0xFF90);
+	__CHECK_SMRAM32_OFFSET(ss,		0xFF9C);
+	__CHECK_SMRAM32_OFFSET(es_sel,		0xFFA8);
+	__CHECK_SMRAM32_OFFSET(cs_sel,		0xFFAC);
+	__CHECK_SMRAM32_OFFSET(ss_sel,		0xFFB0);
+	__CHECK_SMRAM32_OFFSET(ds_sel,		0xFFB4);
+	__CHECK_SMRAM32_OFFSET(fs_sel,		0xFFB8);
+	__CHECK_SMRAM32_OFFSET(gs_sel,		0xFFBC);
+	__CHECK_SMRAM32_OFFSET(ldtr_sel,	0xFFC0);
+	__CHECK_SMRAM32_OFFSET(tr_sel,		0xFFC4);
+	__CHECK_SMRAM32_OFFSET(dr7,		0xFFC8);
+	__CHECK_SMRAM32_OFFSET(dr6,		0xFFCC);
+	__CHECK_SMRAM32_OFFSET(gprs,		0xFFD0);
+	__CHECK_SMRAM32_OFFSET(eip,		0xFFF0);
+	__CHECK_SMRAM32_OFFSET(eflags,		0xFFF4);
+	__CHECK_SMRAM32_OFFSET(cr3,		0xFFF8);
+	__CHECK_SMRAM32_OFFSET(cr0,		0xFFFC);
+#undef __CHECK_SMRAM32_OFFSET
+}
+
+
+/* 64 bit KVM's emulated SMM layout. Based on AMD64 layout */
+
+struct kvm_smm_seg_state_64 {
+	u16 selector;
+	u16 attributes;
+	u32 limit;
+	u64 base;
+};
+
+struct kvm_smram_state_64 {
+
+	struct kvm_smm_seg_state_64 es;
+	struct kvm_smm_seg_state_64 cs;
+	struct kvm_smm_seg_state_64 ss;
+	struct kvm_smm_seg_state_64 ds;
+	struct kvm_smm_seg_state_64 fs;
+	struct kvm_smm_seg_state_64 gs;
+	struct kvm_smm_seg_state_64 gdtr; /* GDTR has only base and limit*/
+	struct kvm_smm_seg_state_64 ldtr;
+	struct kvm_smm_seg_state_64 idtr; /* IDTR has only base and limit*/
+	struct kvm_smm_seg_state_64 tr;
+
+	/* I/O restart and auto halt restart are not implemented by KVM */
+	u64 io_restart_rip;
+	u64 io_restart_rcx;
+	u64 io_restart_rsi;
+	u64 io_restart_rdi;
+	u32 io_restart_dword;
+	u32 reserved1;
+	u8 io_inst_restart;
+	u8 auto_hlt_restart;
+	u8 reserved2[6];
+
+	u64 efer;
+
+	/*
+	 * Two fields below are implemented on AMD only, to store
+	 * SVM guest vmcb address if the #SMI was received while in the guest mode.
+	 */
+	u64 svm_guest_flag;
+	u64 svm_guest_vmcb_gpa;
+	u64 svm_guest_virtual_int; /* unknown purpose, not implemented */
+
+	u32 reserved3[3];
+	u32 smm_revison;
+	u32 smbase;
+	u32 reserved4[5];
+
+	/* ssp and svm_* fields below are not implemented by KVM */
+	u64 ssp;
+	u64 svm_guest_pat;
+	u64 svm_host_efer;
+	u64 svm_host_cr4;
+	u64 svm_host_cr3;
+	u64 svm_host_cr0;
+
+	u64 cr4;
+	u64 cr3;
+	u64 cr0;
+	u64 dr7;
+	u64 dr6;
+	u64 rflags;
+	u64 rip;
+	u64 gprs[16]; /* GPRS in a reversed "natural" X86 order (R15/R14/../RCX/RAX.) */
+};
+
+
+static inline void __check_smram64_offsets(void)
+{
+#define __CHECK_SMRAM64_OFFSET(field, offset) \
+	ASSERT_STRUCT_OFFSET(struct kvm_smram_state_64, field, offset - 0xFE00)
+
+	__CHECK_SMRAM64_OFFSET(es,			0xFE00);
+	__CHECK_SMRAM64_OFFSET(cs,			0xFE10);
+	__CHECK_SMRAM64_OFFSET(ss,			0xFE20);
+	__CHECK_SMRAM64_OFFSET(ds,			0xFE30);
+	__CHECK_SMRAM64_OFFSET(fs,			0xFE40);
+	__CHECK_SMRAM64_OFFSET(gs,			0xFE50);
+	__CHECK_SMRAM64_OFFSET(gdtr,			0xFE60);
+	__CHECK_SMRAM64_OFFSET(ldtr,			0xFE70);
+	__CHECK_SMRAM64_OFFSET(idtr,			0xFE80);
+	__CHECK_SMRAM64_OFFSET(tr,			0xFE90);
+	__CHECK_SMRAM64_OFFSET(io_restart_rip,		0xFEA0);
+	__CHECK_SMRAM64_OFFSET(io_restart_rcx,		0xFEA8);
+	__CHECK_SMRAM64_OFFSET(io_restart_rsi,		0xFEB0);
+	__CHECK_SMRAM64_OFFSET(io_restart_rdi,		0xFEB8);
+	__CHECK_SMRAM64_OFFSET(io_restart_dword,	0xFEC0);
+	__CHECK_SMRAM64_OFFSET(reserved1,		0xFEC4);
+	__CHECK_SMRAM64_OFFSET(io_inst_restart,		0xFEC8);
+	__CHECK_SMRAM64_OFFSET(auto_hlt_restart,	0xFEC9);
+	__CHECK_SMRAM64_OFFSET(reserved2,		0xFECA);
+	__CHECK_SMRAM64_OFFSET(efer,			0xFED0);
+	__CHECK_SMRAM64_OFFSET(svm_guest_flag,		0xFED8);
+	__CHECK_SMRAM64_OFFSET(svm_guest_vmcb_gpa,	0xFEE0);
+	__CHECK_SMRAM64_OFFSET(svm_guest_virtual_int,	0xFEE8);
+	__CHECK_SMRAM64_OFFSET(reserved3,		0xFEF0);
+	__CHECK_SMRAM64_OFFSET(smm_revison,		0xFEFC);
+	__CHECK_SMRAM64_OFFSET(smbase,			0xFF00);
+	__CHECK_SMRAM64_OFFSET(reserved4,		0xFF04);
+	__CHECK_SMRAM64_OFFSET(ssp,			0xFF18);
+	__CHECK_SMRAM64_OFFSET(svm_guest_pat,		0xFF20);
+	__CHECK_SMRAM64_OFFSET(svm_host_efer,		0xFF28);
+	__CHECK_SMRAM64_OFFSET(svm_host_cr4,		0xFF30);
+	__CHECK_SMRAM64_OFFSET(svm_host_cr3,		0xFF38);
+	__CHECK_SMRAM64_OFFSET(svm_host_cr0,		0xFF40);
+	__CHECK_SMRAM64_OFFSET(cr4,			0xFF48);
+	__CHECK_SMRAM64_OFFSET(cr3,			0xFF50);
+	__CHECK_SMRAM64_OFFSET(cr0,			0xFF58);
+	__CHECK_SMRAM64_OFFSET(dr7,			0xFF60);
+	__CHECK_SMRAM64_OFFSET(dr6,			0xFF68);
+	__CHECK_SMRAM64_OFFSET(rflags,			0xFF70);
+	__CHECK_SMRAM64_OFFSET(rip,			0xFF78);
+	__CHECK_SMRAM64_OFFSET(gprs,			0xFF80);
+#undef __CHECK_SMRAM64_OFFSET
+}
+
+union kvm_smram {
+	struct kvm_smram_state_64 smram64;
+	struct kvm_smram_state_32 smram32;
+	u8 bytes[512];
+};
+
+void  __init kvm_emulator_init(void);
+
+
 /* Host execution mode. */
 #if defined(CONFIG_X86_32)
 #define X86EMUL_MODE_HOST X86EMUL_MODE_PROT32
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 33560bfa0cac6e..bea7e5015d592e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -13355,6 +13355,7 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_vmgexit_msr_protocol_exit);
 static int __init kvm_x86_init(void)
 {
 	kvm_mmu_x86_module_init();
+	kvm_emulator_init();
 	return 0;
 }
 module_init(kvm_x86_init);
-- 
2.26.3

Re: [PATCH v3 07/13] KVM: x86: emulator/smm: add structs for KVM's smram layout

[Sean Christopherson]

On Wed, Aug 03, 2022, Maxim Levitsky wrote:
> Those structs will be used to read/write the smram state image.
> 
> Also document the differences between KVM's SMRAM layout and SMRAM
> layout that is used by real Intel/AMD cpus.
> 
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> ---
>  arch/x86/kvm/emulate.c     |   6 +
>  arch/x86/kvm/kvm_emulate.h | 218 +++++++++++++++++++++++++++++++++++++
>  arch/x86/kvm/x86.c         |   1 +
>  3 files changed, 225 insertions(+)
> 
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index 18551611cb13af..55d9328e6074a2 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -5864,3 +5864,9 @@ bool emulator_can_use_gpa(struct x86_emulate_ctxt *ctxt)
>  
>  	return true;
>  }
> +
> +void  __init kvm_emulator_init(void)
> +{
> +	__check_smram32_offsets();
> +	__check_smram64_offsets();
> +}

...

> +static inline void __check_smram64_offsets(void)

Why double underscores?  Same question for the macros.

> +{
> +#define __CHECK_SMRAM64_OFFSET(field, offset) \
> +	ASSERT_STRUCT_OFFSET(struct kvm_smram_state_64, field, offset - 0xFE00)
> +
> +	__CHECK_SMRAM64_OFFSET(es,			0xFE00);
> +	__CHECK_SMRAM64_OFFSET(cs,			0xFE10);
> +	__CHECK_SMRAM64_OFFSET(ss,			0xFE20);
> +	__CHECK_SMRAM64_OFFSET(ds,			0xFE30);
> +	__CHECK_SMRAM64_OFFSET(fs,			0xFE40);
> +	__CHECK_SMRAM64_OFFSET(gs,			0xFE50);
> +	__CHECK_SMRAM64_OFFSET(gdtr,			0xFE60);
> +	__CHECK_SMRAM64_OFFSET(ldtr,			0xFE70);
> +	__CHECK_SMRAM64_OFFSET(idtr,			0xFE80);
> +	__CHECK_SMRAM64_OFFSET(tr,			0xFE90);
> +	__CHECK_SMRAM64_OFFSET(io_restart_rip,		0xFEA0);
> +	__CHECK_SMRAM64_OFFSET(io_restart_rcx,		0xFEA8);
> +	__CHECK_SMRAM64_OFFSET(io_restart_rsi,		0xFEB0);
> +	__CHECK_SMRAM64_OFFSET(io_restart_rdi,		0xFEB8);
> +	__CHECK_SMRAM64_OFFSET(io_restart_dword,	0xFEC0);
> +	__CHECK_SMRAM64_OFFSET(reserved1,		0xFEC4);
> +	__CHECK_SMRAM64_OFFSET(io_inst_restart,		0xFEC8);
> +	__CHECK_SMRAM64_OFFSET(auto_hlt_restart,	0xFEC9);
> +	__CHECK_SMRAM64_OFFSET(reserved2,		0xFECA);
> +	__CHECK_SMRAM64_OFFSET(efer,			0xFED0);
> +	__CHECK_SMRAM64_OFFSET(svm_guest_flag,		0xFED8);
> +	__CHECK_SMRAM64_OFFSET(svm_guest_vmcb_gpa,	0xFEE0);
> +	__CHECK_SMRAM64_OFFSET(svm_guest_virtual_int,	0xFEE8);
> +	__CHECK_SMRAM64_OFFSET(reserved3,		0xFEF0);
> +	__CHECK_SMRAM64_OFFSET(smm_revison,		0xFEFC);
> +	__CHECK_SMRAM64_OFFSET(smbase,			0xFF00);
> +	__CHECK_SMRAM64_OFFSET(reserved4,		0xFF04);
> +	__CHECK_SMRAM64_OFFSET(ssp,			0xFF18);
> +	__CHECK_SMRAM64_OFFSET(svm_guest_pat,		0xFF20);
> +	__CHECK_SMRAM64_OFFSET(svm_host_efer,		0xFF28);
> +	__CHECK_SMRAM64_OFFSET(svm_host_cr4,		0xFF30);
> +	__CHECK_SMRAM64_OFFSET(svm_host_cr3,		0xFF38);
> +	__CHECK_SMRAM64_OFFSET(svm_host_cr0,		0xFF40);
> +	__CHECK_SMRAM64_OFFSET(cr4,			0xFF48);
> +	__CHECK_SMRAM64_OFFSET(cr3,			0xFF50);
> +	__CHECK_SMRAM64_OFFSET(cr0,			0xFF58);
> +	__CHECK_SMRAM64_OFFSET(dr7,			0xFF60);
> +	__CHECK_SMRAM64_OFFSET(dr6,			0xFF68);
> +	__CHECK_SMRAM64_OFFSET(rflags,			0xFF70);
> +	__CHECK_SMRAM64_OFFSET(rip,			0xFF78);
> +	__CHECK_SMRAM64_OFFSET(gprs,			0xFF80);
> +#undef __CHECK_SMRAM64_OFFSET
> +}
> +
> +union kvm_smram {
> +	struct kvm_smram_state_64 smram64;
> +	struct kvm_smram_state_32 smram32;
> +	u8 bytes[512];
> +};
> +
> +void  __init kvm_emulator_init(void);
> +
> +

Unnecessary newline.

>  /* Host execution mode. */
>  #if defined(CONFIG_X86_32)
>  #define X86EMUL_MODE_HOST X86EMUL_MODE_PROT32
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 33560bfa0cac6e..bea7e5015d592e 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -13355,6 +13355,7 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_vmgexit_msr_protocol_exit);
>  static int __init kvm_x86_init(void)
>  {
>  	kvm_mmu_x86_module_init();
> +	kvm_emulator_init();

Please don't add an init call that is nop at runtime, e.g. I was _really_ curious
what initialization needed to be done in the emulator.  And it makes it look like
kvm_x86_exit() forgot to call kvm_emulator_exit().

em_rsm() already ends up with

	BUILD_BUG_ON(sizeof(smram) != 512);

just put all the assertions there.

>  	return 0;
>  }
>  module_init(kvm_x86_init);
> -- 
> 2.26.3
> 

[PATCH v3 08/13] KVM: x86: emulator/smm: use smram structs in the common code

[Maxim Levitsky]

Switch from using a raw array to 'union kvm_smram'.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 arch/x86/include/asm/kvm_host.h |  5 +++--
 arch/x86/kvm/emulate.c          | 12 +++++++-----
 arch/x86/kvm/kvm_emulate.h      |  3 ++-
 arch/x86/kvm/svm/svm.c          |  8 ++++++--
 arch/x86/kvm/vmx/vmx.c          |  4 ++--
 arch/x86/kvm/x86.c              | 16 ++++++++--------
 6 files changed, 28 insertions(+), 20 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index e8281d64a4315a..d752fabde94ad2 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -204,6 +204,7 @@ typedef enum exit_fastpath_completion fastpath_t;
 
 struct x86_emulate_ctxt;
 struct x86_exception;
+union kvm_smram;
 enum x86_intercept;
 enum x86_intercept_stage;
 
@@ -1600,8 +1601,8 @@ struct kvm_x86_ops {
 	void (*setup_mce)(struct kvm_vcpu *vcpu);
 
 	int (*smi_allowed)(struct kvm_vcpu *vcpu, bool for_injection);
-	int (*enter_smm)(struct kvm_vcpu *vcpu, char *smstate);
-	int (*leave_smm)(struct kvm_vcpu *vcpu, const char *smstate);
+	int (*enter_smm)(struct kvm_vcpu *vcpu, union kvm_smram *smram);
+	int (*leave_smm)(struct kvm_vcpu *vcpu, const union kvm_smram *smram);
 	void (*enable_smi_window)(struct kvm_vcpu *vcpu);
 
 	int (*mem_enc_ioctl)(struct kvm *kvm, void __user *argp);
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 55d9328e6074a2..610978d00b52b0 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2594,16 +2594,18 @@ static int rsm_load_state_64(struct x86_emulate_ctxt *ctxt,
 static int em_rsm(struct x86_emulate_ctxt *ctxt)
 {
 	unsigned long cr0, cr4, efer;
-	char buf[512];
+	const union kvm_smram smram;
 	u64 smbase;
 	int ret;
 
+	BUILD_BUG_ON(sizeof(smram) != 512);
+
 	if ((ctxt->ops->get_hflags(ctxt) & X86EMUL_SMM_MASK) == 0)
 		return emulate_ud(ctxt);
 
 	smbase = ctxt->ops->get_smbase(ctxt);
 
-	ret = ctxt->ops->read_phys(ctxt, smbase + 0xfe00, buf, sizeof(buf));
+	ret = ctxt->ops->read_phys(ctxt, smbase + 0xfe00, (void *)&smram, sizeof(smram));
 	if (ret != X86EMUL_CONTINUE)
 		return X86EMUL_UNHANDLEABLE;
 
@@ -2653,15 +2655,15 @@ static int em_rsm(struct x86_emulate_ctxt *ctxt)
 	 * state (e.g. enter guest mode) before loading state from the SMM
 	 * state-save area.
 	 */
-	if (ctxt->ops->leave_smm(ctxt, buf))
+	if (ctxt->ops->leave_smm(ctxt, &smram))
 		goto emulate_shutdown;
 
 #ifdef CONFIG_X86_64
 	if (emulator_has_longmode(ctxt))
-		ret = rsm_load_state_64(ctxt, buf);
+		ret = rsm_load_state_64(ctxt, (const char *)&smram);
 	else
 #endif
-		ret = rsm_load_state_32(ctxt, buf);
+		ret = rsm_load_state_32(ctxt, (const char *)&smram);
 
 	if (ret != X86EMUL_CONTINUE)
 		goto emulate_shutdown;
diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
index dd0ae61e44a116..76c0b8e7890b5d 100644
--- a/arch/x86/kvm/kvm_emulate.h
+++ b/arch/x86/kvm/kvm_emulate.h
@@ -19,6 +19,7 @@
 struct x86_emulate_ctxt;
 enum x86_intercept;
 enum x86_intercept_stage;
+union kvm_smram;
 
 struct x86_exception {
 	u8 vector;
@@ -236,7 +237,7 @@ struct x86_emulate_ops {
 
 	unsigned (*get_hflags)(struct x86_emulate_ctxt *ctxt);
 	void (*exiting_smm)(struct x86_emulate_ctxt *ctxt);
-	int (*leave_smm)(struct x86_emulate_ctxt *ctxt, const char *smstate);
+	int (*leave_smm)(struct x86_emulate_ctxt *ctxt, const union kvm_smram *smram);
 	void (*triple_fault)(struct x86_emulate_ctxt *ctxt);
 	int (*set_xcr)(struct x86_emulate_ctxt *ctxt, u32 index, u64 xcr);
 };
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 38f873cb6f2c14..688315d1dfabd1 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4433,12 +4433,14 @@ static int svm_smi_allowed(struct kvm_vcpu *vcpu, bool for_injection)
 	return 1;
 }
 
-static int svm_enter_smm(struct kvm_vcpu *vcpu, char *smstate)
+static int svm_enter_smm(struct kvm_vcpu *vcpu, union kvm_smram *smram)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
 	struct kvm_host_map map_save;
 	int ret;
 
+	char *smstate = (char *)smram;
+
 	if (!is_guest_mode(vcpu))
 		return 0;
 
@@ -4480,7 +4482,7 @@ static int svm_enter_smm(struct kvm_vcpu *vcpu, char *smstate)
 	return 0;
 }
 
-static int svm_leave_smm(struct kvm_vcpu *vcpu, const char *smstate)
+static int svm_leave_smm(struct kvm_vcpu *vcpu, const union kvm_smram *smram)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
 	struct kvm_host_map map, map_save;
@@ -4488,6 +4490,8 @@ static int svm_leave_smm(struct kvm_vcpu *vcpu, const char *smstate)
 	struct vmcb *vmcb12;
 	int ret;
 
+	const char *smstate = (const char *)smram;
+
 	if (!guest_cpuid_has(vcpu, X86_FEATURE_LM))
 		return 0;
 
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index d7f8331d6f7e72..fdb7e9280e9150 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7919,7 +7919,7 @@ static int vmx_smi_allowed(struct kvm_vcpu *vcpu, bool for_injection)
 	return !is_smm(vcpu);
 }
 
-static int vmx_enter_smm(struct kvm_vcpu *vcpu, char *smstate)
+static int vmx_enter_smm(struct kvm_vcpu *vcpu, union kvm_smram *smram)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 
@@ -7940,7 +7940,7 @@ static int vmx_enter_smm(struct kvm_vcpu *vcpu, char *smstate)
 	return 0;
 }
 
-static int vmx_leave_smm(struct kvm_vcpu *vcpu, const char *smstate)
+static int vmx_leave_smm(struct kvm_vcpu *vcpu, const union kvm_smram *smram)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	int ret;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index bea7e5015d592e..cbbe49bdc58787 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8054,9 +8054,9 @@ static void emulator_exiting_smm(struct x86_emulate_ctxt *ctxt)
 }
 
 static int emulator_leave_smm(struct x86_emulate_ctxt *ctxt,
-				  const char *smstate)
+			      const union kvm_smram *smram)
 {
-	return static_call(kvm_x86_leave_smm)(emul_to_vcpu(ctxt), smstate);
+	return static_call(kvm_x86_leave_smm)(emul_to_vcpu(ctxt), smram);
 }
 
 static void emulator_triple_fault(struct x86_emulate_ctxt *ctxt)
@@ -9979,25 +9979,25 @@ static void enter_smm(struct kvm_vcpu *vcpu)
 	struct kvm_segment cs, ds;
 	struct desc_ptr dt;
 	unsigned long cr0;
-	char buf[512];
+	union kvm_smram smram;
 
-	memset(buf, 0, 512);
+	memset(smram.bytes, 0, sizeof(smram.bytes));
 #ifdef CONFIG_X86_64
 	if (guest_cpuid_has(vcpu, X86_FEATURE_LM))
-		enter_smm_save_state_64(vcpu, buf);
+		enter_smm_save_state_64(vcpu, (char *)&smram);
 	else
 #endif
-		enter_smm_save_state_32(vcpu, buf);
+		enter_smm_save_state_32(vcpu, (char *)&smram);
 
 	/*
 	 * Give enter_smm() a chance to make ISA-specific changes to the vCPU
 	 * state (e.g. leave guest mode) after we've saved the state into the
 	 * SMM state-save area.
 	 */
-	static_call(kvm_x86_enter_smm)(vcpu, buf);
+	static_call(kvm_x86_enter_smm)(vcpu, &smram);
 
 	kvm_smm_changed(vcpu, true);
-	kvm_vcpu_write_guest(vcpu, vcpu->arch.smbase + 0xfe00, buf, sizeof(buf));
+	kvm_vcpu_write_guest(vcpu, vcpu->arch.smbase + 0xfe00, &smram, sizeof(smram));
 
 	if (static_call(kvm_x86_get_nmi_mask)(vcpu))
 		vcpu->arch.hflags |= HF_SMM_INSIDE_NMI_MASK;
-- 
2.26.3

Re: [PATCH v3 08/13] KVM: x86: emulator/smm: use smram structs in the common code

[Sean Christopherson]

On Wed, Aug 03, 2022, Maxim Levitsky wrote:
> Switch from using a raw array to 'union kvm_smram'.
> 
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> ---
>  arch/x86/include/asm/kvm_host.h |  5 +++--
>  arch/x86/kvm/emulate.c          | 12 +++++++-----
>  arch/x86/kvm/kvm_emulate.h      |  3 ++-
>  arch/x86/kvm/svm/svm.c          |  8 ++++++--
>  arch/x86/kvm/vmx/vmx.c          |  4 ++--
>  arch/x86/kvm/x86.c              | 16 ++++++++--------
>  6 files changed, 28 insertions(+), 20 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index e8281d64a4315a..d752fabde94ad2 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -204,6 +204,7 @@ typedef enum exit_fastpath_completion fastpath_t;
>  
>  struct x86_emulate_ctxt;
>  struct x86_exception;
> +union kvm_smram;
>  enum x86_intercept;
>  enum x86_intercept_stage;
>  
> @@ -1600,8 +1601,8 @@ struct kvm_x86_ops {
>  	void (*setup_mce)(struct kvm_vcpu *vcpu);
>  
>  	int (*smi_allowed)(struct kvm_vcpu *vcpu, bool for_injection);
> -	int (*enter_smm)(struct kvm_vcpu *vcpu, char *smstate);
> -	int (*leave_smm)(struct kvm_vcpu *vcpu, const char *smstate);
> +	int (*enter_smm)(struct kvm_vcpu *vcpu, union kvm_smram *smram);
> +	int (*leave_smm)(struct kvm_vcpu *vcpu, const union kvm_smram *smram);
>  	void (*enable_smi_window)(struct kvm_vcpu *vcpu);
>  
>  	int (*mem_enc_ioctl)(struct kvm *kvm, void __user *argp);
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index 55d9328e6074a2..610978d00b52b0 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -2594,16 +2594,18 @@ static int rsm_load_state_64(struct x86_emulate_ctxt *ctxt,
>  static int em_rsm(struct x86_emulate_ctxt *ctxt)
>  {
>  	unsigned long cr0, cr4, efer;
> -	char buf[512];
> +	const union kvm_smram smram;

This is blatantly wrong, ctxt->ops->read_phys() writes to the buffer.  I assume
you did this to make it more difficult to modify the buffer after reading from
guest memory, but IMO that's not worth misleading readers.

>  	u64 smbase;
>  	int ret;
>  
> +	BUILD_BUG_ON(sizeof(smram) != 512);
> +
>  	if ((ctxt->ops->get_hflags(ctxt) & X86EMUL_SMM_MASK) == 0)
>  		return emulate_ud(ctxt);
>  
>  	smbase = ctxt->ops->get_smbase(ctxt);
>  
> -	ret = ctxt->ops->read_phys(ctxt, smbase + 0xfe00, buf, sizeof(buf));
> +	ret = ctxt->ops->read_phys(ctxt, smbase + 0xfe00, (void *)&smram, sizeof(smram));

The point of the union + bytes is so that KVM doesn't have to cast.

	kvm_vcpu_write_guest(vcpu, vcpu->arch.smbase + 0xfe00,
			     smram.bytes, sizeof(smram));

>  	if (ret != X86EMUL_CONTINUE)
>  		return X86EMUL_UNHANDLEABLE;
>  
> @@ -2653,15 +2655,15 @@ static int em_rsm(struct x86_emulate_ctxt *ctxt)
>  	 * state (e.g. enter guest mode) before loading state from the SMM
>  	 * state-save area.
>  	 */
> -	if (ctxt->ops->leave_smm(ctxt, buf))
> +	if (ctxt->ops->leave_smm(ctxt, &smram))
>  		goto emulate_shutdown;
>  
>  #ifdef CONFIG_X86_64
>  	if (emulator_has_longmode(ctxt))
> -		ret = rsm_load_state_64(ctxt, buf);
> +		ret = rsm_load_state_64(ctxt, (const char *)&smram);
>  	else
>  #endif
> -		ret = rsm_load_state_32(ctxt, buf);
> +		ret = rsm_load_state_32(ctxt, (const char *)&smram);

Same thing here, though this is temporary.  And it's kinda silly, but I think it
makes sense to avoid the cast here by tweaking the rsm_load_state_*() helpers to
take "u8 *" instead of "char *".

>  	if (ret != X86EMUL_CONTINUE)
>  		goto emulate_shutdown;

> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 38f873cb6f2c14..688315d1dfabd1 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -4433,12 +4433,14 @@ static int svm_smi_allowed(struct kvm_vcpu *vcpu, bool for_injection)
>  	return 1;
>  }
>  
> -static int svm_enter_smm(struct kvm_vcpu *vcpu, char *smstate)
> +static int svm_enter_smm(struct kvm_vcpu *vcpu, union kvm_smram *smram)
>  {
>  	struct vcpu_svm *svm = to_svm(vcpu);
>  	struct kvm_host_map map_save;
>  	int ret;
>  
> +	char *smstate = (char *)smram;

Again temporary, but since this is new code, just make it

	u8 *smstate = smram->bytes;

> +
>  	if (!is_guest_mode(vcpu))
>  		return 0;
>  
> @@ -4480,7 +4482,7 @@ static int svm_enter_smm(struct kvm_vcpu *vcpu, char *smstate)
>  	return 0;
>  }
>  
> -static int svm_leave_smm(struct kvm_vcpu *vcpu, const char *smstate)
> +static int svm_leave_smm(struct kvm_vcpu *vcpu, const union kvm_smram *smram)
>  {
>  	struct vcpu_svm *svm = to_svm(vcpu);
>  	struct kvm_host_map map, map_save;
> @@ -4488,6 +4490,8 @@ static int svm_leave_smm(struct kvm_vcpu *vcpu, const char *smstate)
>  	struct vmcb *vmcb12;
>  	int ret;
>  
> +	const char *smstate = (const char *)smram;
> +

And here.

>  	if (!guest_cpuid_has(vcpu, X86_FEATURE_LM))
>  		return 0;
>  

E.g. this compiles cleanly on top

---
 arch/x86/kvm/emulate.c | 17 +++++++++--------
 arch/x86/kvm/svm/svm.c |  4 ++--
 arch/x86/kvm/x86.c     |  7 ++++---
 3 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index dd0a08af1dd9..b2ef63cf6cff 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2357,7 +2357,7 @@ static void rsm_set_desc_flags(struct desc_struct *desc, u32 flags)
 	desc->type = (flags >>  8) & 15;
 }

-static int rsm_load_seg_32(struct x86_emulate_ctxt *ctxt, const char *smstate,
+static int rsm_load_seg_32(struct x86_emulate_ctxt *ctxt, const u8 *smstate,
 			   int n)
 {
 	struct desc_struct desc;
@@ -2379,7 +2379,7 @@ static int rsm_load_seg_32(struct x86_emulate_ctxt *ctxt, const char *smstate,
 }

 #ifdef CONFIG_X86_64
-static int rsm_load_seg_64(struct x86_emulate_ctxt *ctxt, const char *smstate,
+static int rsm_load_seg_64(struct x86_emulate_ctxt *ctxt, const u8 *smstate,
 			   int n)
 {
 	struct desc_struct desc;
@@ -2446,7 +2446,7 @@ static int rsm_enter_protected_mode(struct x86_emulate_ctxt *ctxt,
 }

 static int rsm_load_state_32(struct x86_emulate_ctxt *ctxt,
-			     const char *smstate)
+			     const u8 *smstate)
 {
 	struct desc_struct desc;
 	struct desc_ptr dt;
@@ -2507,7 +2507,7 @@ static int rsm_load_state_32(struct x86_emulate_ctxt *ctxt,

 #ifdef CONFIG_X86_64
 static int rsm_load_state_64(struct x86_emulate_ctxt *ctxt,
-			     const char *smstate)
+			     const u8 *smstate)
 {
 	struct desc_struct desc;
 	struct desc_ptr dt;
@@ -2580,7 +2580,7 @@ static int rsm_load_state_64(struct x86_emulate_ctxt *ctxt,
 static int em_rsm(struct x86_emulate_ctxt *ctxt)
 {
 	unsigned long cr0, cr4, efer;
-	const union kvm_smram smram;
+	union kvm_smram smram;
 	u64 smbase;
 	int ret;

@@ -2591,7 +2591,8 @@ static int em_rsm(struct x86_emulate_ctxt *ctxt)

 	smbase = ctxt->ops->get_smbase(ctxt);

-	ret = ctxt->ops->read_phys(ctxt, smbase + 0xfe00, (void *)&smram, sizeof(smram));
+	ret = ctxt->ops->read_phys(ctxt, smbase + 0xfe00,
+				   smram.bytes, sizeof(smram));
 	if (ret != X86EMUL_CONTINUE)
 		return X86EMUL_UNHANDLEABLE;

@@ -2646,10 +2647,10 @@ static int em_rsm(struct x86_emulate_ctxt *ctxt)

 #ifdef CONFIG_X86_64
 	if (emulator_has_longmode(ctxt))
-		ret = rsm_load_state_64(ctxt, (const char *)&smram);
+		ret = rsm_load_state_64(ctxt, smram.bytes);
 	else
 #endif
-		ret = rsm_load_state_32(ctxt, (const char *)&smram);
+		ret = rsm_load_state_32(ctxt, smram.bytes);

 	if (ret != X86EMUL_CONTINUE)
 		goto emulate_shutdown;
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 5d748b10c5be..ecf11c8a052e 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4439,7 +4439,7 @@ static int svm_enter_smm(struct kvm_vcpu *vcpu, union kvm_smram *smram)
 	struct kvm_host_map map_save;
 	int ret;

-	char *smstate = (char *)smram;
+	u8 *smstate = smram->bytes;

 	if (!is_guest_mode(vcpu))
 		return 0;
@@ -4490,7 +4490,7 @@ static int svm_leave_smm(struct kvm_vcpu *vcpu, const union kvm_smram *smram)
 	struct vmcb *vmcb12;
 	int ret;

-	const char *smstate = (const char *)smram;
+	const char *smstate = smram->bytes;

 	if (!guest_cpuid_has(vcpu, X86_FEATURE_LM))
 		return 0;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ca558674b07b..09268c2335a8 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9985,10 +9985,10 @@ static void enter_smm(struct kvm_vcpu *vcpu)
 	memset(smram.bytes, 0, sizeof(smram.bytes));
 #ifdef CONFIG_X86_64
 	if (guest_cpuid_has(vcpu, X86_FEATURE_LM))
-		enter_smm_save_state_64(vcpu, (char *)&smram);
+		enter_smm_save_state_64(vcpu, smram.bytes);
 	else
 #endif
-		enter_smm_save_state_32(vcpu, (char *)&smram);
+		enter_smm_save_state_32(vcpu, smram.bytes);

 	/*
 	 * Give enter_smm() a chance to make ISA-specific changes to the vCPU
@@ -9998,7 +9998,8 @@ static void enter_smm(struct kvm_vcpu *vcpu)
 	static_call(kvm_x86_enter_smm)(vcpu, &smram);

 	kvm_smm_changed(vcpu, true);
-	kvm_vcpu_write_guest(vcpu, vcpu->arch.smbase + 0xfe00, &smram, sizeof(smram));
+	kvm_vcpu_write_guest(vcpu, vcpu->arch.smbase + 0xfe00,
+			     smram.bytes, sizeof(smram));

 	if (static_call(kvm_x86_get_nmi_mask)(vcpu))
 		vcpu->arch.hflags |= HF_SMM_INSIDE_NMI_MASK;

base-commit: 0708faef18ff51a2b2dba546961d843223331138
--

[PATCH v3 09/13] KVM: x86: emulator/smm: use smram struct for 32 bit smram load/restore

[Maxim Levitsky]

Use kvm_smram_state_32 struct to save/restore 32 bit SMM state
(used when X86_FEATURE_LM is not present in the guest CPUID).

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 arch/x86/kvm/emulate.c | 81 +++++++++++++++---------------------------
 arch/x86/kvm/x86.c     | 75 +++++++++++++++++---------------------
 2 files changed, 60 insertions(+), 96 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 610978d00b52b0..3339d542a25439 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2371,25 +2371,17 @@ static void rsm_set_desc_flags(struct desc_struct *desc, u32 flags)
 	desc->type = (flags >>  8) & 15;
 }
 
-static int rsm_load_seg_32(struct x86_emulate_ctxt *ctxt, const char *smstate,
+static void rsm_load_seg_32(struct x86_emulate_ctxt *ctxt,
+			   const struct kvm_smm_seg_state_32 *state,
+			   u16 selector,
 			   int n)
 {
 	struct desc_struct desc;
-	int offset;
-	u16 selector;
-
-	selector = GET_SMSTATE(u32, smstate, 0x7fa8 + n * 4);
-
-	if (n < 3)
-		offset = 0x7f84 + n * 12;
-	else
-		offset = 0x7f2c + (n - 3) * 12;
 
-	set_desc_base(&desc,      GET_SMSTATE(u32, smstate, offset + 8));
-	set_desc_limit(&desc,     GET_SMSTATE(u32, smstate, offset + 4));
-	rsm_set_desc_flags(&desc, GET_SMSTATE(u32, smstate, offset));
+	set_desc_base(&desc,      state->base);
+	set_desc_limit(&desc,     state->limit);
+	rsm_set_desc_flags(&desc, state->flags);
 	ctxt->ops->set_segment(ctxt, selector, &desc, 0, n);
-	return X86EMUL_CONTINUE;
 }
 
 #ifdef CONFIG_X86_64
@@ -2460,63 +2452,46 @@ static int rsm_enter_protected_mode(struct x86_emulate_ctxt *ctxt,
 }
 
 static int rsm_load_state_32(struct x86_emulate_ctxt *ctxt,
-			     const char *smstate)
+			     const struct kvm_smram_state_32 *smstate)
 {
-	struct desc_struct desc;
 	struct desc_ptr dt;
-	u16 selector;
-	u32 val, cr0, cr3, cr4;
 	int i;
 
-	cr0 =                      GET_SMSTATE(u32, smstate, 0x7ffc);
-	cr3 =                      GET_SMSTATE(u32, smstate, 0x7ff8);
-	ctxt->eflags =             GET_SMSTATE(u32, smstate, 0x7ff4) | X86_EFLAGS_FIXED;
-	ctxt->_eip =               GET_SMSTATE(u32, smstate, 0x7ff0);
+	ctxt->eflags =  smstate->eflags | X86_EFLAGS_FIXED;
+	ctxt->_eip =  smstate->eip;
 
 	for (i = 0; i < 8; i++)
-		*reg_write(ctxt, i) = GET_SMSTATE(u32, smstate, 0x7fd0 + i * 4);
-
-	val = GET_SMSTATE(u32, smstate, 0x7fcc);
+		*reg_write(ctxt, i) = smstate->gprs[i];
 
-	if (ctxt->ops->set_dr(ctxt, 6, val))
+	if (ctxt->ops->set_dr(ctxt, 6, smstate->dr6))
 		return X86EMUL_UNHANDLEABLE;
-
-	val = GET_SMSTATE(u32, smstate, 0x7fc8);
-
-	if (ctxt->ops->set_dr(ctxt, 7, val))
+	if (ctxt->ops->set_dr(ctxt, 7, smstate->dr7))
 		return X86EMUL_UNHANDLEABLE;
 
-	selector =                 GET_SMSTATE(u32, smstate, 0x7fc4);
-	set_desc_base(&desc,       GET_SMSTATE(u32, smstate, 0x7f64));
-	set_desc_limit(&desc,      GET_SMSTATE(u32, smstate, 0x7f60));
-	rsm_set_desc_flags(&desc,  GET_SMSTATE(u32, smstate, 0x7f5c));
-	ctxt->ops->set_segment(ctxt, selector, &desc, 0, VCPU_SREG_TR);
+	rsm_load_seg_32(ctxt, &smstate->tr, smstate->tr_sel, VCPU_SREG_TR);
+	rsm_load_seg_32(ctxt, &smstate->ldtr, smstate->ldtr_sel, VCPU_SREG_LDTR);
 
-	selector =                 GET_SMSTATE(u32, smstate, 0x7fc0);
-	set_desc_base(&desc,       GET_SMSTATE(u32, smstate, 0x7f80));
-	set_desc_limit(&desc,      GET_SMSTATE(u32, smstate, 0x7f7c));
-	rsm_set_desc_flags(&desc,  GET_SMSTATE(u32, smstate, 0x7f78));
-	ctxt->ops->set_segment(ctxt, selector, &desc, 0, VCPU_SREG_LDTR);
 
-	dt.address =               GET_SMSTATE(u32, smstate, 0x7f74);
-	dt.size =                  GET_SMSTATE(u32, smstate, 0x7f70);
+	dt.address =               smstate->gdtr.base;
+	dt.size =                  smstate->gdtr.limit;
 	ctxt->ops->set_gdt(ctxt, &dt);
 
-	dt.address =               GET_SMSTATE(u32, smstate, 0x7f58);
-	dt.size =                  GET_SMSTATE(u32, smstate, 0x7f54);
+	dt.address =               smstate->idtr.base;
+	dt.size =                  smstate->idtr.limit;
 	ctxt->ops->set_idt(ctxt, &dt);
 
-	for (i = 0; i < 6; i++) {
-		int r = rsm_load_seg_32(ctxt, smstate, i);
-		if (r != X86EMUL_CONTINUE)
-			return r;
-	}
+	rsm_load_seg_32(ctxt, &smstate->es, smstate->es_sel, VCPU_SREG_ES);
+	rsm_load_seg_32(ctxt, &smstate->cs, smstate->cs_sel, VCPU_SREG_CS);
+	rsm_load_seg_32(ctxt, &smstate->ss, smstate->ss_sel, VCPU_SREG_SS);
 
-	cr4 = GET_SMSTATE(u32, smstate, 0x7f14);
+	rsm_load_seg_32(ctxt, &smstate->ds, smstate->ds_sel, VCPU_SREG_DS);
+	rsm_load_seg_32(ctxt, &smstate->fs, smstate->fs_sel, VCPU_SREG_FS);
+	rsm_load_seg_32(ctxt, &smstate->gs, smstate->gs_sel, VCPU_SREG_GS);
 
-	ctxt->ops->set_smbase(ctxt, GET_SMSTATE(u32, smstate, 0x7ef8));
+	ctxt->ops->set_smbase(ctxt, smstate->smbase);
 
-	return rsm_enter_protected_mode(ctxt, cr0, cr3, cr4);
+	return rsm_enter_protected_mode(ctxt, smstate->cr0,
+					smstate->cr3, smstate->cr4);
 }
 
 #ifdef CONFIG_X86_64
@@ -2663,7 +2638,7 @@ static int em_rsm(struct x86_emulate_ctxt *ctxt)
 		ret = rsm_load_state_64(ctxt, (const char *)&smram);
 	else
 #endif
-		ret = rsm_load_state_32(ctxt, (const char *)&smram);
+		ret = rsm_load_state_32(ctxt, &smram.smram32);
 
 	if (ret != X86EMUL_CONTINUE)
 		goto emulate_shutdown;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index cbbe49bdc58787..6abe35f7687e2c 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9833,22 +9833,18 @@ static u32 enter_smm_get_segment_flags(struct kvm_segment *seg)
 	return flags;
 }
 
-static void enter_smm_save_seg_32(struct kvm_vcpu *vcpu, char *buf, int n)
+static void enter_smm_save_seg_32(struct kvm_vcpu *vcpu,
+					 struct kvm_smm_seg_state_32 *state,
+					 u32 *selector,
+					 int n)
 {
 	struct kvm_segment seg;
-	int offset;
 
 	kvm_get_segment(vcpu, &seg, n);
-	put_smstate(u32, buf, 0x7fa8 + n * 4, seg.selector);
-
-	if (n < 3)
-		offset = 0x7f84 + n * 12;
-	else
-		offset = 0x7f2c + (n - 3) * 12;
-
-	put_smstate(u32, buf, offset + 8, seg.base);
-	put_smstate(u32, buf, offset + 4, seg.limit);
-	put_smstate(u32, buf, offset, enter_smm_get_segment_flags(&seg));
+	*selector = seg.selector;
+	state->base = seg.base;
+	state->limit = seg.limit;
+	state->flags = enter_smm_get_segment_flags(&seg);
 }
 
 #ifdef CONFIG_X86_64
@@ -9869,54 +9865,47 @@ static void enter_smm_save_seg_64(struct kvm_vcpu *vcpu, char *buf, int n)
 }
 #endif
 
-static void enter_smm_save_state_32(struct kvm_vcpu *vcpu, char *buf)
+static void enter_smm_save_state_32(struct kvm_vcpu *vcpu, struct kvm_smram_state_32 *smram)
 {
 	struct desc_ptr dt;
-	struct kvm_segment seg;
 	unsigned long val;
 	int i;
 
-	put_smstate(u32, buf, 0x7ffc, kvm_read_cr0(vcpu));
-	put_smstate(u32, buf, 0x7ff8, kvm_read_cr3(vcpu));
-	put_smstate(u32, buf, 0x7ff4, kvm_get_rflags(vcpu));
-	put_smstate(u32, buf, 0x7ff0, kvm_rip_read(vcpu));
+	smram->cr0     = kvm_read_cr0(vcpu);
+	smram->cr3     = kvm_read_cr3(vcpu);
+	smram->eflags  = kvm_get_rflags(vcpu);
+	smram->eip     = kvm_rip_read(vcpu);
 
 	for (i = 0; i < 8; i++)
-		put_smstate(u32, buf, 0x7fd0 + i * 4, kvm_register_read_raw(vcpu, i));
+		smram->gprs[i] = kvm_register_read_raw(vcpu, i);
 
 	kvm_get_dr(vcpu, 6, &val);
-	put_smstate(u32, buf, 0x7fcc, (u32)val);
+	smram->dr6     = (u32)val;
 	kvm_get_dr(vcpu, 7, &val);
-	put_smstate(u32, buf, 0x7fc8, (u32)val);
+	smram->dr7     = (u32)val;
 
-	kvm_get_segment(vcpu, &seg, VCPU_SREG_TR);
-	put_smstate(u32, buf, 0x7fc4, seg.selector);
-	put_smstate(u32, buf, 0x7f64, seg.base);
-	put_smstate(u32, buf, 0x7f60, seg.limit);
-	put_smstate(u32, buf, 0x7f5c, enter_smm_get_segment_flags(&seg));
-
-	kvm_get_segment(vcpu, &seg, VCPU_SREG_LDTR);
-	put_smstate(u32, buf, 0x7fc0, seg.selector);
-	put_smstate(u32, buf, 0x7f80, seg.base);
-	put_smstate(u32, buf, 0x7f7c, seg.limit);
-	put_smstate(u32, buf, 0x7f78, enter_smm_get_segment_flags(&seg));
+	enter_smm_save_seg_32(vcpu, &smram->tr, &smram->tr_sel, VCPU_SREG_TR);
+	enter_smm_save_seg_32(vcpu, &smram->ldtr, &smram->ldtr_sel, VCPU_SREG_LDTR);
 
 	static_call(kvm_x86_get_gdt)(vcpu, &dt);
-	put_smstate(u32, buf, 0x7f74, dt.address);
-	put_smstate(u32, buf, 0x7f70, dt.size);
+	smram->gdtr.base = dt.address;
+	smram->gdtr.limit = dt.size;
 
 	static_call(kvm_x86_get_idt)(vcpu, &dt);
-	put_smstate(u32, buf, 0x7f58, dt.address);
-	put_smstate(u32, buf, 0x7f54, dt.size);
+	smram->idtr.base = dt.address;
+	smram->idtr.limit = dt.size;
 
-	for (i = 0; i < 6; i++)
-		enter_smm_save_seg_32(vcpu, buf, i);
+	enter_smm_save_seg_32(vcpu, &smram->es, &smram->es_sel, VCPU_SREG_ES);
+	enter_smm_save_seg_32(vcpu, &smram->cs, &smram->cs_sel, VCPU_SREG_CS);
+	enter_smm_save_seg_32(vcpu, &smram->ss, &smram->ss_sel, VCPU_SREG_SS);
 
-	put_smstate(u32, buf, 0x7f14, kvm_read_cr4(vcpu));
+	enter_smm_save_seg_32(vcpu, &smram->ds, &smram->ds_sel, VCPU_SREG_DS);
+	enter_smm_save_seg_32(vcpu, &smram->fs, &smram->fs_sel, VCPU_SREG_FS);
+	enter_smm_save_seg_32(vcpu, &smram->gs, &smram->gs_sel, VCPU_SREG_GS);
 
-	/* revision id */
-	put_smstate(u32, buf, 0x7efc, 0x00020000);
-	put_smstate(u32, buf, 0x7ef8, vcpu->arch.smbase);
+	smram->cr4 = kvm_read_cr4(vcpu);
+	smram->smm_revision = 0x00020000;
+	smram->smbase = vcpu->arch.smbase;
 }
 
 #ifdef CONFIG_X86_64
@@ -9987,7 +9976,7 @@ static void enter_smm(struct kvm_vcpu *vcpu)
 		enter_smm_save_state_64(vcpu, (char *)&smram);
 	else
 #endif
-		enter_smm_save_state_32(vcpu, (char *)&smram);
+		enter_smm_save_state_32(vcpu, &smram.smram32);
 
 	/*
 	 * Give enter_smm() a chance to make ISA-specific changes to the vCPU
-- 
2.26.3

Re: [PATCH v3 09/13] KVM: x86: emulator/smm: use smram struct for 32 bit smram load/restore

[Sean Christopherson]

On Wed, Aug 03, 2022, Maxim Levitsky wrote:
> Use kvm_smram_state_32 struct to save/restore 32 bit SMM state
> (used when X86_FEATURE_LM is not present in the guest CPUID).
> 
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> ---
>  arch/x86/kvm/emulate.c | 81 +++++++++++++++---------------------------
>  arch/x86/kvm/x86.c     | 75 +++++++++++++++++---------------------
>  2 files changed, 60 insertions(+), 96 deletions(-)
> 
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index 610978d00b52b0..3339d542a25439 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -2371,25 +2371,17 @@ static void rsm_set_desc_flags(struct desc_struct *desc, u32 flags)
>  	desc->type = (flags >>  8) & 15;
>  }
>  
> -static int rsm_load_seg_32(struct x86_emulate_ctxt *ctxt, const char *smstate,
> +static void rsm_load_seg_32(struct x86_emulate_ctxt *ctxt,
> +			   const struct kvm_smm_seg_state_32 *state,

Alignment is off by one.

> +			   u16 selector,
>  			   int n)

These can go on a single line.

static void rsm_load_seg_32(struct x86_emulate_ctxt *ctxt,
			    const struct kvm_smm_seg_state_32 *state,
			    u16 selector, int n)

>  	struct desc_struct desc;
> -	int offset;
> -	u16 selector;
> -
> -	selector = GET_SMSTATE(u32, smstate, 0x7fa8 + n * 4);
> -
> -	if (n < 3)
> -		offset = 0x7f84 + n * 12;
> -	else
> -		offset = 0x7f2c + (n - 3) * 12;
>  
> -	set_desc_base(&desc,      GET_SMSTATE(u32, smstate, offset + 8));
> -	set_desc_limit(&desc,     GET_SMSTATE(u32, smstate, offset + 4));
> -	rsm_set_desc_flags(&desc, GET_SMSTATE(u32, smstate, offset));
> +	set_desc_base(&desc,      state->base);
> +	set_desc_limit(&desc,     state->limit);
> +	rsm_set_desc_flags(&desc, state->flags);
>  	ctxt->ops->set_segment(ctxt, selector, &desc, 0, n);
> -	return X86EMUL_CONTINUE;
>  }
>  

...

> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index cbbe49bdc58787..6abe35f7687e2c 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -9833,22 +9833,18 @@ static u32 enter_smm_get_segment_flags(struct kvm_segment *seg)
>  	return flags;
>  }
>  
> -static void enter_smm_save_seg_32(struct kvm_vcpu *vcpu, char *buf, int n)
> +static void enter_smm_save_seg_32(struct kvm_vcpu *vcpu,
> +					 struct kvm_smm_seg_state_32 *state,
> +					 u32 *selector,
> +					 int n)

Similar issues here.

static void enter_smm_save_seg_32(struct kvm_vcpu *vcpu,
				  struct kvm_smm_seg_state_32 *state,
				  u32 *selector, int n)
>  {
>  	struct kvm_segment seg;
> -	int offset;
>  
>  	kvm_get_segment(vcpu, &seg, n);
> -	put_smstate(u32, buf, 0x7fa8 + n * 4, seg.selector);
> -
> -	if (n < 3)
> -		offset = 0x7f84 + n * 12;
> -	else
> -		offset = 0x7f2c + (n - 3) * 12;
> -
> -	put_smstate(u32, buf, offset + 8, seg.base);
> -	put_smstate(u32, buf, offset + 4, seg.limit);
> -	put_smstate(u32, buf, offset, enter_smm_get_segment_flags(&seg));
> +	*selector = seg.selector;
> +	state->base = seg.base;
> +	state->limit = seg.limit;
> +	state->flags = enter_smm_get_segment_flags(&seg);
>  }
>  
>  #ifdef CONFIG_X86_64
> @@ -9869,54 +9865,47 @@ static void enter_smm_save_seg_64(struct kvm_vcpu *vcpu, char *buf, int n)
>  }
>  #endif
>  
> -static void enter_smm_save_state_32(struct kvm_vcpu *vcpu, char *buf)
> +static void enter_smm_save_state_32(struct kvm_vcpu *vcpu, struct kvm_smram_state_32 *smram)

Please wrap, no reason to run long.

static void enter_smm_save_state_32(struct kvm_vcpu *vcpu,
				    struct kvm_smram_state_32 *smram)

[PATCH v3 10/13] KVM: x86: emulator/smm: use smram struct for 64 bit smram load/restore

[Maxim Levitsky]

Use kvm_smram_state_64 struct to save/restore the 64 bit SMM state
(used when X86_FEATURE_LM is present in the guest CPUID,
regardless of 32-bitness of the guest).

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 arch/x86/kvm/emulate.c | 88 ++++++++++++++----------------------------
 arch/x86/kvm/x86.c     | 75 ++++++++++++++++-------------------
 2 files changed, 62 insertions(+), 101 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 3339d542a25439..4bdbc5893a1657 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2385,24 +2385,16 @@ static void rsm_load_seg_32(struct x86_emulate_ctxt *ctxt,
 }
 
 #ifdef CONFIG_X86_64
-static int rsm_load_seg_64(struct x86_emulate_ctxt *ctxt, const char *smstate,
-			   int n)
+static void rsm_load_seg_64(struct x86_emulate_ctxt *ctxt,
+			    const struct kvm_smm_seg_state_64 *state,
+			    int n)
 {
 	struct desc_struct desc;
-	int offset;
-	u16 selector;
-	u32 base3;
-
-	offset = 0x7e00 + n * 16;
-
-	selector =                GET_SMSTATE(u16, smstate, offset);
-	rsm_set_desc_flags(&desc, GET_SMSTATE(u16, smstate, offset + 2) << 8);
-	set_desc_limit(&desc,     GET_SMSTATE(u32, smstate, offset + 4));
-	set_desc_base(&desc,      GET_SMSTATE(u32, smstate, offset + 8));
-	base3 =                   GET_SMSTATE(u32, smstate, offset + 12);
 
-	ctxt->ops->set_segment(ctxt, selector, &desc, base3, n);
-	return X86EMUL_CONTINUE;
+	rsm_set_desc_flags(&desc, state->attributes << 8);
+	set_desc_limit(&desc,     state->limit);
+	set_desc_base(&desc,      (u32)state->base);
+	ctxt->ops->set_segment(ctxt, state->selector, &desc, state->base >> 32, n);
 }
 #endif
 
@@ -2496,71 +2488,49 @@ static int rsm_load_state_32(struct x86_emulate_ctxt *ctxt,
 
 #ifdef CONFIG_X86_64
 static int rsm_load_state_64(struct x86_emulate_ctxt *ctxt,
-			     const char *smstate)
+			     const struct kvm_smram_state_64 *smstate)
 {
-	struct desc_struct desc;
 	struct desc_ptr dt;
-	u64 val, cr0, cr3, cr4;
-	u32 base3;
-	u16 selector;
 	int i, r;
 
 	for (i = 0; i < 16; i++)
-		*reg_write(ctxt, i) = GET_SMSTATE(u64, smstate, 0x7ff8 - i * 8);
+		*reg_write(ctxt, i) = smstate->gprs[15 - i];
 
-	ctxt->_eip   = GET_SMSTATE(u64, smstate, 0x7f78);
-	ctxt->eflags = GET_SMSTATE(u32, smstate, 0x7f70) | X86_EFLAGS_FIXED;
+	ctxt->_eip   = smstate->rip;
+	ctxt->eflags = smstate->rflags | X86_EFLAGS_FIXED;
 
-	val = GET_SMSTATE(u64, smstate, 0x7f68);
-
-	if (ctxt->ops->set_dr(ctxt, 6, val))
+	if (ctxt->ops->set_dr(ctxt, 6, smstate->dr6))
 		return X86EMUL_UNHANDLEABLE;
-
-	val = GET_SMSTATE(u64, smstate, 0x7f60);
-
-	if (ctxt->ops->set_dr(ctxt, 7, val))
+	if (ctxt->ops->set_dr(ctxt, 7, smstate->dr7))
 		return X86EMUL_UNHANDLEABLE;
 
-	cr0 =                       GET_SMSTATE(u64, smstate, 0x7f58);
-	cr3 =                       GET_SMSTATE(u64, smstate, 0x7f50);
-	cr4 =                       GET_SMSTATE(u64, smstate, 0x7f48);
-	ctxt->ops->set_smbase(ctxt, GET_SMSTATE(u32, smstate, 0x7f00));
-	val =                       GET_SMSTATE(u64, smstate, 0x7ed0);
+	ctxt->ops->set_smbase(ctxt, smstate->smbase);
 
-	if (ctxt->ops->set_msr(ctxt, MSR_EFER, val & ~EFER_LMA))
+	if (ctxt->ops->set_msr(ctxt, MSR_EFER, smstate->efer & ~EFER_LMA))
 		return X86EMUL_UNHANDLEABLE;
 
-	selector =                  GET_SMSTATE(u32, smstate, 0x7e90);
-	rsm_set_desc_flags(&desc,   GET_SMSTATE(u32, smstate, 0x7e92) << 8);
-	set_desc_limit(&desc,       GET_SMSTATE(u32, smstate, 0x7e94));
-	set_desc_base(&desc,        GET_SMSTATE(u32, smstate, 0x7e98));
-	base3 =                     GET_SMSTATE(u32, smstate, 0x7e9c);
-	ctxt->ops->set_segment(ctxt, selector, &desc, base3, VCPU_SREG_TR);
+	rsm_load_seg_64(ctxt, &smstate->tr, VCPU_SREG_TR);
 
-	dt.size =                   GET_SMSTATE(u32, smstate, 0x7e84);
-	dt.address =                GET_SMSTATE(u64, smstate, 0x7e88);
+	dt.size =                   smstate->idtr.limit;
+	dt.address =                smstate->idtr.base;
 	ctxt->ops->set_idt(ctxt, &dt);
 
-	selector =                  GET_SMSTATE(u32, smstate, 0x7e70);
-	rsm_set_desc_flags(&desc,   GET_SMSTATE(u32, smstate, 0x7e72) << 8);
-	set_desc_limit(&desc,       GET_SMSTATE(u32, smstate, 0x7e74));
-	set_desc_base(&desc,        GET_SMSTATE(u32, smstate, 0x7e78));
-	base3 =                     GET_SMSTATE(u32, smstate, 0x7e7c);
-	ctxt->ops->set_segment(ctxt, selector, &desc, base3, VCPU_SREG_LDTR);
+	rsm_load_seg_64(ctxt, &smstate->ldtr, VCPU_SREG_LDTR);
 
-	dt.size =                   GET_SMSTATE(u32, smstate, 0x7e64);
-	dt.address =                GET_SMSTATE(u64, smstate, 0x7e68);
+	dt.size =                   smstate->gdtr.limit;
+	dt.address =                smstate->gdtr.base;
 	ctxt->ops->set_gdt(ctxt, &dt);
 
-	r = rsm_enter_protected_mode(ctxt, cr0, cr3, cr4);
+	r = rsm_enter_protected_mode(ctxt, smstate->cr0, smstate->cr3, smstate->cr4);
 	if (r != X86EMUL_CONTINUE)
 		return r;
 
-	for (i = 0; i < 6; i++) {
-		r = rsm_load_seg_64(ctxt, smstate, i);
-		if (r != X86EMUL_CONTINUE)
-			return r;
-	}
+	rsm_load_seg_64(ctxt, &smstate->es, VCPU_SREG_ES);
+	rsm_load_seg_64(ctxt, &smstate->cs, VCPU_SREG_CS);
+	rsm_load_seg_64(ctxt, &smstate->ss, VCPU_SREG_SS);
+	rsm_load_seg_64(ctxt, &smstate->ds, VCPU_SREG_DS);
+	rsm_load_seg_64(ctxt, &smstate->fs, VCPU_SREG_FS);
+	rsm_load_seg_64(ctxt, &smstate->gs, VCPU_SREG_GS);
 
 	return X86EMUL_CONTINUE;
 }
@@ -2635,7 +2605,7 @@ static int em_rsm(struct x86_emulate_ctxt *ctxt)
 
 #ifdef CONFIG_X86_64
 	if (emulator_has_longmode(ctxt))
-		ret = rsm_load_state_64(ctxt, (const char *)&smram);
+		ret = rsm_load_state_64(ctxt, &smram.smram64);
 	else
 #endif
 		ret = rsm_load_state_32(ctxt, &smram.smram32);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 6abe35f7687e2c..4e3ef63baf83df 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9848,20 +9848,17 @@ static void enter_smm_save_seg_32(struct kvm_vcpu *vcpu,
 }
 
 #ifdef CONFIG_X86_64
-static void enter_smm_save_seg_64(struct kvm_vcpu *vcpu, char *buf, int n)
+static void enter_smm_save_seg_64(struct kvm_vcpu *vcpu,
+				  struct kvm_smm_seg_state_64 *state,
+				  int n)
 {
 	struct kvm_segment seg;
-	int offset;
-	u16 flags;
 
 	kvm_get_segment(vcpu, &seg, n);
-	offset = 0x7e00 + n * 16;
-
-	flags = enter_smm_get_segment_flags(&seg) >> 8;
-	put_smstate(u16, buf, offset, seg.selector);
-	put_smstate(u16, buf, offset + 2, flags);
-	put_smstate(u32, buf, offset + 4, seg.limit);
-	put_smstate(u64, buf, offset + 8, seg.base);
+	state->selector = seg.selector;
+	state->attributes = enter_smm_get_segment_flags(&seg) >> 8;
+	state->limit = seg.limit;
+	state->base = seg.base;
 }
 #endif
 
@@ -9909,57 +9906,51 @@ static void enter_smm_save_state_32(struct kvm_vcpu *vcpu, struct kvm_smram_stat
 }
 
 #ifdef CONFIG_X86_64
-static void enter_smm_save_state_64(struct kvm_vcpu *vcpu, char *buf)
+static void enter_smm_save_state_64(struct kvm_vcpu *vcpu, struct kvm_smram_state_64 *smram)
 {
 	struct desc_ptr dt;
-	struct kvm_segment seg;
 	unsigned long val;
 	int i;
 
 	for (i = 0; i < 16; i++)
-		put_smstate(u64, buf, 0x7ff8 - i * 8, kvm_register_read_raw(vcpu, i));
+		smram->gprs[15 - i] = kvm_register_read_raw(vcpu, i);
+
+	smram->rip    = kvm_rip_read(vcpu);
+	smram->rflags = kvm_get_rflags(vcpu);
 
-	put_smstate(u64, buf, 0x7f78, kvm_rip_read(vcpu));
-	put_smstate(u32, buf, 0x7f70, kvm_get_rflags(vcpu));
 
 	kvm_get_dr(vcpu, 6, &val);
-	put_smstate(u64, buf, 0x7f68, val);
+	smram->dr6 = val;
 	kvm_get_dr(vcpu, 7, &val);
-	put_smstate(u64, buf, 0x7f60, val);
-
-	put_smstate(u64, buf, 0x7f58, kvm_read_cr0(vcpu));
-	put_smstate(u64, buf, 0x7f50, kvm_read_cr3(vcpu));
-	put_smstate(u64, buf, 0x7f48, kvm_read_cr4(vcpu));
+	smram->dr7 = val;
 
-	put_smstate(u32, buf, 0x7f00, vcpu->arch.smbase);
+	smram->cr0 = kvm_read_cr0(vcpu);
+	smram->cr3 = kvm_read_cr3(vcpu);
+	smram->cr4 = kvm_read_cr4(vcpu);
 
-	/* revision id */
-	put_smstate(u32, buf, 0x7efc, 0x00020064);
+	smram->smbase = vcpu->arch.smbase;
+	smram->smm_revison = 0x00020064;
 
-	put_smstate(u64, buf, 0x7ed0, vcpu->arch.efer);
+	smram->efer = vcpu->arch.efer;
 
-	kvm_get_segment(vcpu, &seg, VCPU_SREG_TR);
-	put_smstate(u16, buf, 0x7e90, seg.selector);
-	put_smstate(u16, buf, 0x7e92, enter_smm_get_segment_flags(&seg) >> 8);
-	put_smstate(u32, buf, 0x7e94, seg.limit);
-	put_smstate(u64, buf, 0x7e98, seg.base);
+	enter_smm_save_seg_64(vcpu, &smram->tr, VCPU_SREG_TR);
 
 	static_call(kvm_x86_get_idt)(vcpu, &dt);
-	put_smstate(u32, buf, 0x7e84, dt.size);
-	put_smstate(u64, buf, 0x7e88, dt.address);
+	smram->idtr.limit = dt.size;
+	smram->idtr.base = dt.address;
 
-	kvm_get_segment(vcpu, &seg, VCPU_SREG_LDTR);
-	put_smstate(u16, buf, 0x7e70, seg.selector);
-	put_smstate(u16, buf, 0x7e72, enter_smm_get_segment_flags(&seg) >> 8);
-	put_smstate(u32, buf, 0x7e74, seg.limit);
-	put_smstate(u64, buf, 0x7e78, seg.base);
+	enter_smm_save_seg_64(vcpu, &smram->ldtr, VCPU_SREG_LDTR);
 
 	static_call(kvm_x86_get_gdt)(vcpu, &dt);
-	put_smstate(u32, buf, 0x7e64, dt.size);
-	put_smstate(u64, buf, 0x7e68, dt.address);
+	smram->gdtr.limit = dt.size;
+	smram->gdtr.base = dt.address;
 
-	for (i = 0; i < 6; i++)
-		enter_smm_save_seg_64(vcpu, buf, i);
+	enter_smm_save_seg_64(vcpu, &smram->es, VCPU_SREG_ES);
+	enter_smm_save_seg_64(vcpu, &smram->cs, VCPU_SREG_CS);
+	enter_smm_save_seg_64(vcpu, &smram->ss, VCPU_SREG_SS);
+	enter_smm_save_seg_64(vcpu, &smram->ds, VCPU_SREG_DS);
+	enter_smm_save_seg_64(vcpu, &smram->fs, VCPU_SREG_FS);
+	enter_smm_save_seg_64(vcpu, &smram->gs, VCPU_SREG_GS);
 }
 #endif
 
@@ -9973,7 +9964,7 @@ static void enter_smm(struct kvm_vcpu *vcpu)
 	memset(smram.bytes, 0, sizeof(smram.bytes));
 #ifdef CONFIG_X86_64
 	if (guest_cpuid_has(vcpu, X86_FEATURE_LM))
-		enter_smm_save_state_64(vcpu, (char *)&smram);
+		enter_smm_save_state_64(vcpu, &smram.smram64);
 	else
 #endif
 		enter_smm_save_state_32(vcpu, &smram.smram32);
-- 
2.26.3

Re: [PATCH v3 10/13] KVM: x86: emulator/smm: use smram struct for 64 bit smram load/restore

[Sean Christopherson]

On Wed, Aug 03, 2022, Maxim Levitsky wrote:
> @@ -9909,57 +9906,51 @@ static void enter_smm_save_state_32(struct kvm_vcpu *vcpu, struct kvm_smram_stat
>  }
>  
>  #ifdef CONFIG_X86_64
> -static void enter_smm_save_state_64(struct kvm_vcpu *vcpu, char *buf)
> +static void enter_smm_save_state_64(struct kvm_vcpu *vcpu, struct kvm_smram_state_64 *smram)

Please put these on different lines.

>  	struct desc_ptr dt;
> -	struct kvm_segment seg;
>  	unsigned long val;
>  	int i;
>  
>  	for (i = 0; i < 16; i++)
> -		put_smstate(u64, buf, 0x7ff8 - i * 8, kvm_register_read_raw(vcpu, i));
> +		smram->gprs[15 - i] = kvm_register_read_raw(vcpu, i);

Blech, why do I get the feeling that the original layout was designed so that
ucode could use PUSHAD?  This look so weird...

[PATCH v3 11/13] KVM: x86: SVM: use smram structs

[Maxim Levitsky]

This removes the last user of put_smstate/GET_SMSTATE so
remove these functions as well.

Also add a sanity check that we don't attempt to enter the SMM
on non long mode capable guest CPU with a running nested guest.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 arch/x86/include/asm/kvm_host.h |  6 ------
 arch/x86/kvm/svm/svm.c          | 21 ++++++---------------
 2 files changed, 6 insertions(+), 21 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index d752fabde94ad2..d570ec522ebb55 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -2077,12 +2077,6 @@ static inline int kvm_cpu_get_apicid(int mps_cpu)
 #endif
 }
 
-#define put_smstate(type, buf, offset, val)                      \
-	*(type *)((buf) + (offset) - 0x7e00) = val
-
-#define GET_SMSTATE(type, buf, offset)		\
-	(*(type *)((buf) + (offset) - 0x7e00))
-
 int kvm_cpu_dirty_log_size(void);
 
 int memslot_rmap_alloc(struct kvm_memory_slot *slot, unsigned long npages);
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 688315d1dfabd1..7ca5e06878e19a 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4439,15 +4439,11 @@ static int svm_enter_smm(struct kvm_vcpu *vcpu, union kvm_smram *smram)
 	struct kvm_host_map map_save;
 	int ret;
 
-	char *smstate = (char *)smram;
-
 	if (!is_guest_mode(vcpu))
 		return 0;
 
-	/* FED8h - SVM Guest */
-	put_smstate(u64, smstate, 0x7ed8, 1);
-	/* FEE0h - SVM Guest VMCB Physical Address */
-	put_smstate(u64, smstate, 0x7ee0, svm->nested.vmcb12_gpa);
+	smram->smram64.svm_guest_flag = 1;
+	smram->smram64.svm_guest_vmcb_gpa = svm->nested.vmcb12_gpa;
 
 	svm->vmcb->save.rax = vcpu->arch.regs[VCPU_REGS_RAX];
 	svm->vmcb->save.rsp = vcpu->arch.regs[VCPU_REGS_RSP];
@@ -4486,28 +4482,23 @@ static int svm_leave_smm(struct kvm_vcpu *vcpu, const union kvm_smram *smram)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
 	struct kvm_host_map map, map_save;
-	u64 saved_efer, vmcb12_gpa;
 	struct vmcb *vmcb12;
 	int ret;
 
-	const char *smstate = (const char *)smram;
-
 	if (!guest_cpuid_has(vcpu, X86_FEATURE_LM))
 		return 0;
 
 	/* Non-zero if SMI arrived while vCPU was in guest mode. */
-	if (!GET_SMSTATE(u64, smstate, 0x7ed8))
+	if (!smram->smram64.svm_guest_flag)
 		return 0;
 
 	if (!guest_cpuid_has(vcpu, X86_FEATURE_SVM))
 		return 1;
 
-	saved_efer = GET_SMSTATE(u64, smstate, 0x7ed0);
-	if (!(saved_efer & EFER_SVME))
+	if (!(smram->smram64.efer & EFER_SVME))
 		return 1;
 
-	vmcb12_gpa = GET_SMSTATE(u64, smstate, 0x7ee0);
-	if (kvm_vcpu_map(vcpu, gpa_to_gfn(vmcb12_gpa), &map) == -EINVAL)
+	if (kvm_vcpu_map(vcpu, gpa_to_gfn(smram->smram64.svm_guest_vmcb_gpa), &map) == -EINVAL)
 		return 1;
 
 	ret = 1;
@@ -4533,7 +4524,7 @@ static int svm_leave_smm(struct kvm_vcpu *vcpu, const union kvm_smram *smram)
 	vmcb12 = map.hva;
 	nested_copy_vmcb_control_to_cache(svm, &vmcb12->control);
 	nested_copy_vmcb_save_to_cache(svm, &vmcb12->save);
-	ret = enter_svm_guest_mode(vcpu, vmcb12_gpa, vmcb12, false);
+	ret = enter_svm_guest_mode(vcpu, smram->smram64.svm_guest_vmcb_gpa, vmcb12, false);
 
 	if (ret)
 		goto unmap_save;
-- 
2.26.3

Re: [PATCH v3 11/13] KVM: x86: SVM: use smram structs

[Sean Christopherson]

On Wed, Aug 03, 2022, Maxim Levitsky wrote:
> @@ -4486,28 +4482,23 @@ static int svm_leave_smm(struct kvm_vcpu *vcpu, const union kvm_smram *smram)
>  {
>  	struct vcpu_svm *svm = to_svm(vcpu);
>  	struct kvm_host_map map, map_save;
> -	u64 saved_efer, vmcb12_gpa;
>  	struct vmcb *vmcb12;
>  	int ret;
>  
> -	const char *smstate = (const char *)smram;

To shorten line lengths, what about grabbing smram64 here?

	const kvm_smram_state_64 *smram64 = &smram->smram64;

IMO, makes things a little easier to read too.

> -
>  	if (!guest_cpuid_has(vcpu, X86_FEATURE_LM))
>  		return 0;
>  
>  	/* Non-zero if SMI arrived while vCPU was in guest mode. */
> -	if (!GET_SMSTATE(u64, smstate, 0x7ed8))
> +	if (!smram->smram64.svm_guest_flag)
>  		return 0;
>  
>  	if (!guest_cpuid_has(vcpu, X86_FEATURE_SVM))
>  		return 1;
>  
> -	saved_efer = GET_SMSTATE(u64, smstate, 0x7ed0);
> -	if (!(saved_efer & EFER_SVME))
> +	if (!(smram->smram64.efer & EFER_SVME))
>  		return 1;
>  
> -	vmcb12_gpa = GET_SMSTATE(u64, smstate, 0x7ee0);
> -	if (kvm_vcpu_map(vcpu, gpa_to_gfn(vmcb12_gpa), &map) == -EINVAL)
> +	if (kvm_vcpu_map(vcpu, gpa_to_gfn(smram->smram64.svm_guest_vmcb_gpa), &map) == -EINVAL)

Eww, this is horrifically wrong.  KVM will explode if kvm_vcpu_map() returns
-EFAULT, e.g. if guest memory is not backed by struct page and memremap() fails.
Not to mention that it's comically fragile too.

Can you add a patch to this series to drop the "== -EINVAL"?

And there's another one lurking just out of sight in this diff.

>  		return 1;
>  
>  	ret = 1;
> @@ -4533,7 +4524,7 @@ static int svm_leave_smm(struct kvm_vcpu *vcpu, const union kvm_smram *smram)
>  	vmcb12 = map.hva;
>  	nested_copy_vmcb_control_to_cache(svm, &vmcb12->control);
>  	nested_copy_vmcb_save_to_cache(svm, &vmcb12->save);
> -	ret = enter_svm_guest_mode(vcpu, vmcb12_gpa, vmcb12, false);
> +	ret = enter_svm_guest_mode(vcpu, smram->smram64.svm_guest_vmcb_gpa, vmcb12, false);
>  
>  	if (ret)
>  		goto unmap_save;
> -- 
> 2.26.3
> 

[PATCH v3 12/13] KVM: x86: SVM: don't save SVM state to SMRAM when VM is not long mode capable

[Maxim Levitsky]

When the guest CPUID doesn't have support for long mode, 32 bit SMRAM
layout is used and it has no support for preserving EFER and/or SVM
state.

Note that this isn't relevant to running 32 bit guests on VM which is
long mode capable - such VM can still run 32 bit guests in compatibility
mode.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 arch/x86/kvm/svm/svm.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 7ca5e06878e19a..64cfd26bc5e7a6 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4442,6 +4442,15 @@ static int svm_enter_smm(struct kvm_vcpu *vcpu, union kvm_smram *smram)
 	if (!is_guest_mode(vcpu))
 		return 0;
 
+	/*
+	 * 32 bit SMRAM format doesn't preserve EFER and SVM state.
+	 * SVM should not be enabled by the userspace without marking
+	 * the CPU as at least long mode capable.
+	 */
+
+	if (!guest_cpuid_has(vcpu, X86_FEATURE_LM))
+		return 1;
+
 	smram->smram64.svm_guest_flag = 1;
 	smram->smram64.svm_guest_vmcb_gpa = svm->nested.vmcb12_gpa;
 
-- 
2.26.3

Re: [PATCH v3 12/13] KVM: x86: SVM: don't save SVM state to SMRAM when VM is not long mode capable

[Sean Christopherson]

On Wed, Aug 03, 2022, Maxim Levitsky wrote:
> When the guest CPUID doesn't have support for long mode, 32 bit SMRAM
> layout is used and it has no support for preserving EFER and/or SVM
> state.
> 
> Note that this isn't relevant to running 32 bit guests on VM which is
> long mode capable - such VM can still run 32 bit guests in compatibility
> mode.
> 
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> ---
>  arch/x86/kvm/svm/svm.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 7ca5e06878e19a..64cfd26bc5e7a6 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -4442,6 +4442,15 @@ static int svm_enter_smm(struct kvm_vcpu *vcpu, union kvm_smram *smram)
>  	if (!is_guest_mode(vcpu))
>  		return 0;
>  
> +	/*
> +	 * 32 bit SMRAM format doesn't preserve EFER and SVM state.
> +	 * SVM should not be enabled by the userspace without marking
> +	 * the CPU as at least long mode capable.

Hmm, or userspace can ensure SMIs never get delivered.  Maybe?

	/*
	 * 32-bit SMRAM format doesn't preserve EFER and SVM state.  Userspace is
	 * responsible for ensuring nested SVM and SMIs are mutually exclusive.
	 */

> +	 */
> +

Unnecessary newline.

> +	if (!guest_cpuid_has(vcpu, X86_FEATURE_LM))
> +		return 1;

This doesn't actually fix anything,  RSM will still jump to L2 state but in L1
context.  I think we first need to actually handle errors from
static_call(kvm_x86_enter_smm).

Given that SVM can't even guarantee nested_svm_simple_vmexit() succeeds, i.e. KVM
can't force the vCPU out of L2 to ensure triple fault would hit L1, killing the VM
seems like the least awful solution (and it's still quite awful).

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 54fa0aa95785..38a6f4089296 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9985,7 +9985,10 @@ static void enter_smm(struct kvm_vcpu *vcpu)
         * state (e.g. leave guest mode) after we've saved the state into the
         * SMM state-save area.
         */
-       static_call(kvm_x86_enter_smm)(vcpu, &smram);
+       if (static_call(kvm_x86_enter_smm)(vcpu, &smram)) {
+               kvm_vm_dead(vcpu->vm);
+               return;
+       }

        kvm_smm_changed(vcpu, true);
        kvm_vcpu_write_guest(vcpu, vcpu->arch.smbase + 0xfe00, &smram, sizeof(smram));

> +
>  	smram->smram64.svm_guest_flag = 1;
>  	smram->smram64.svm_guest_vmcb_gpa = svm->nested.vmcb12_gpa;
>  
> -- 
> 2.26.3
> 

[PATCH v3 13/13] KVM: x86: emulator/smm: preserve interrupt shadow in SMRAM

[Maxim Levitsky]

When #SMI is asserted, the CPU can be in interrupt shadow
due to sti or mov ss.

It is not mandatory in  Intel/AMD prm to have the #SMI
blocked during the shadow, and on top of
that, since neither SVM nor VMX has true support for SMI
window, waiting for one instruction would mean single stepping
the guest.

Instead, allow #SMI in this case, but both reset the interrupt
window and stash its value in SMRAM to restore it on exit
from SMM.

This fixes rare failures seen mostly on windows guests on VMX,
when #SMI falls on the sti instruction which mainfest in
VM entry failure due to EFLAGS.IF not being set, but STI interrupt
window still being set in the VMCS.


Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 arch/x86/kvm/emulate.c     | 17 ++++++++++++++---
 arch/x86/kvm/kvm_emulate.h | 10 ++++++----
 arch/x86/kvm/x86.c         | 12 ++++++++++++
 3 files changed, 32 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 4bdbc5893a1657..b4bc45cec3249d 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2447,7 +2447,7 @@ static int rsm_load_state_32(struct x86_emulate_ctxt *ctxt,
 			     const struct kvm_smram_state_32 *smstate)
 {
 	struct desc_ptr dt;
-	int i;
+	int i, r;
 
 	ctxt->eflags =  smstate->eflags | X86_EFLAGS_FIXED;
 	ctxt->_eip =  smstate->eip;
@@ -2482,8 +2482,16 @@ static int rsm_load_state_32(struct x86_emulate_ctxt *ctxt,
 
 	ctxt->ops->set_smbase(ctxt, smstate->smbase);
 
-	return rsm_enter_protected_mode(ctxt, smstate->cr0,
-					smstate->cr3, smstate->cr4);
+	r = rsm_enter_protected_mode(ctxt, smstate->cr0,
+				     smstate->cr3, smstate->cr4);
+
+	if (r != X86EMUL_CONTINUE)
+		return r;
+
+	ctxt->ops->set_int_shadow(ctxt, 0);
+	ctxt->interruptibility = (u8)smstate->int_shadow;
+
+	return X86EMUL_CONTINUE;
 }
 
 #ifdef CONFIG_X86_64
@@ -2532,6 +2540,9 @@ static int rsm_load_state_64(struct x86_emulate_ctxt *ctxt,
 	rsm_load_seg_64(ctxt, &smstate->fs, VCPU_SREG_FS);
 	rsm_load_seg_64(ctxt, &smstate->gs, VCPU_SREG_GS);
 
+	ctxt->ops->set_int_shadow(ctxt, 0);
+	ctxt->interruptibility = (u8)smstate->int_shadow;
+
 	return X86EMUL_CONTINUE;
 }
 #endif
diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
index 76c0b8e7890b5d..a7313add0f2a58 100644
--- a/arch/x86/kvm/kvm_emulate.h
+++ b/arch/x86/kvm/kvm_emulate.h
@@ -234,6 +234,7 @@ struct x86_emulate_ops {
 	bool (*guest_has_rdpid)(struct x86_emulate_ctxt *ctxt);
 
 	void (*set_nmi_mask)(struct x86_emulate_ctxt *ctxt, bool masked);
+	void (*set_int_shadow)(struct x86_emulate_ctxt *ctxt, u8 shadow);
 
 	unsigned (*get_hflags)(struct x86_emulate_ctxt *ctxt);
 	void (*exiting_smm)(struct x86_emulate_ctxt *ctxt);
@@ -518,7 +519,8 @@ struct kvm_smram_state_32 {
 	u32 reserved1[62];
 	u32 smbase;
 	u32 smm_revision;
-	u32 reserved2[5];
+	u32 reserved2[4];
+	u32 int_shadow; /* KVM extension */
 	u32 cr4; /* CR4 is not present in Intel/AMD SMRAM image */
 	u32 reserved3[5];
 
@@ -566,6 +568,7 @@ static inline void __check_smram32_offsets(void)
 	__CHECK_SMRAM32_OFFSET(smbase,		0xFEF8);
 	__CHECK_SMRAM32_OFFSET(smm_revision,	0xFEFC);
 	__CHECK_SMRAM32_OFFSET(reserved2,	0xFF00);
+	__CHECK_SMRAM32_OFFSET(int_shadow,	0xFF10);
 	__CHECK_SMRAM32_OFFSET(cr4,		0xFF14);
 	__CHECK_SMRAM32_OFFSET(reserved3,	0xFF18);
 	__CHECK_SMRAM32_OFFSET(ds,		0xFF2C);
@@ -625,7 +628,7 @@ struct kvm_smram_state_64 {
 	u64 io_restart_rsi;
 	u64 io_restart_rdi;
 	u32 io_restart_dword;
-	u32 reserved1;
+	u32 int_shadow;
 	u8 io_inst_restart;
 	u8 auto_hlt_restart;
 	u8 reserved2[6];
@@ -663,7 +666,6 @@ struct kvm_smram_state_64 {
 	u64 gprs[16]; /* GPRS in a reversed "natural" X86 order (R15/R14/../RCX/RAX.) */
 };
 
-
 static inline void __check_smram64_offsets(void)
 {
 #define __CHECK_SMRAM64_OFFSET(field, offset) \
@@ -684,7 +686,7 @@ static inline void __check_smram64_offsets(void)
 	__CHECK_SMRAM64_OFFSET(io_restart_rsi,		0xFEB0);
 	__CHECK_SMRAM64_OFFSET(io_restart_rdi,		0xFEB8);
 	__CHECK_SMRAM64_OFFSET(io_restart_dword,	0xFEC0);
-	__CHECK_SMRAM64_OFFSET(reserved1,		0xFEC4);
+	__CHECK_SMRAM64_OFFSET(int_shadow,		0xFEC4);
 	__CHECK_SMRAM64_OFFSET(io_inst_restart,		0xFEC8);
 	__CHECK_SMRAM64_OFFSET(auto_hlt_restart,	0xFEC9);
 	__CHECK_SMRAM64_OFFSET(reserved2,		0xFECA);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4e3ef63baf83df..ae4c20cec7a9fc 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8041,6 +8041,11 @@ static void emulator_set_nmi_mask(struct x86_emulate_ctxt *ctxt, bool masked)
 	static_call(kvm_x86_set_nmi_mask)(emul_to_vcpu(ctxt), masked);
 }
 
+static void emulator_set_int_shadow(struct x86_emulate_ctxt *ctxt, u8 shadow)
+{
+	 static_call(kvm_x86_set_interrupt_shadow)(emul_to_vcpu(ctxt), shadow);
+}
+
 static unsigned emulator_get_hflags(struct x86_emulate_ctxt *ctxt)
 {
 	return emul_to_vcpu(ctxt)->arch.hflags;
@@ -8121,6 +8126,7 @@ static const struct x86_emulate_ops emulate_ops = {
 	.guest_has_fxsr      = emulator_guest_has_fxsr,
 	.guest_has_rdpid     = emulator_guest_has_rdpid,
 	.set_nmi_mask        = emulator_set_nmi_mask,
+	.set_int_shadow      = emulator_set_int_shadow,
 	.get_hflags          = emulator_get_hflags,
 	.exiting_smm         = emulator_exiting_smm,
 	.leave_smm           = emulator_leave_smm,
@@ -9903,6 +9909,8 @@ static void enter_smm_save_state_32(struct kvm_vcpu *vcpu, struct kvm_smram_stat
 	smram->cr4 = kvm_read_cr4(vcpu);
 	smram->smm_revision = 0x00020000;
 	smram->smbase = vcpu->arch.smbase;
+
+	smram->int_shadow = static_call(kvm_x86_get_interrupt_shadow)(vcpu);
 }
 
 #ifdef CONFIG_X86_64
@@ -9951,6 +9959,8 @@ static void enter_smm_save_state_64(struct kvm_vcpu *vcpu, struct kvm_smram_stat
 	enter_smm_save_seg_64(vcpu, &smram->ds, VCPU_SREG_DS);
 	enter_smm_save_seg_64(vcpu, &smram->fs, VCPU_SREG_FS);
 	enter_smm_save_seg_64(vcpu, &smram->gs, VCPU_SREG_GS);
+
+	smram->int_shadow = static_call(kvm_x86_get_interrupt_shadow)(vcpu);
 }
 #endif
 
@@ -9987,6 +9997,8 @@ static void enter_smm(struct kvm_vcpu *vcpu)
 	kvm_set_rflags(vcpu, X86_EFLAGS_FIXED);
 	kvm_rip_write(vcpu, 0x8000);
 
+	static_call(kvm_x86_set_interrupt_shadow)(vcpu, 0);
+
 	cr0 = vcpu->arch.cr0 & ~(X86_CR0_PE | X86_CR0_EM | X86_CR0_TS | X86_CR0_PG);
 	static_call(kvm_x86_set_cr0)(vcpu, cr0);
 	vcpu->arch.cr0 = cr0;
-- 
2.26.3

Re: [PATCH v3 13/13] KVM: x86: emulator/smm: preserve interrupt shadow in SMRAM

[Sean Christopherson]

On Wed, Aug 03, 2022, Maxim Levitsky wrote:
> @@ -518,7 +519,8 @@ struct kvm_smram_state_32 {
>  	u32 reserved1[62];
>  	u32 smbase;
>  	u32 smm_revision;
> -	u32 reserved2[5];
> +	u32 reserved2[4];
> +	u32 int_shadow; /* KVM extension */

Looking at this with fresh(er) eyes, I agree with Jim: KVM shouldn't add its own
fields in SMRAM.  There's no need to use vmcb/vmcs memory either, just add fields
in kvm_vcpu_arch to save/restore the state across SMI/RSM, and then borrow VMX's
approach of supporting migration by adding flags to do out-of-band migration,
e.g. KVM_STATE_NESTED_SMM_STI_BLOCKING and KVM_STATE_NESTED_SMM_MOV_SS_BLOCKING.

	/* SMM state that's not saved in SMRAM. */
	struct {
		struct {
			u8 interruptibility;
		} smm;
	} nested;

That'd finally give us an excuse to move nested_run_pending to common code too :-)

Re: [PATCH v3 13/13] KVM: x86: emulator/smm: preserve interrupt shadow in SMRAM

[Maxim Levitsky]

On Wed, 2022-08-24 at 23:50 +0000, Sean Christopherson wrote:
> On Wed, Aug 03, 2022, Maxim Levitsky wrote:
> > @@ -518,7 +519,8 @@ struct kvm_smram_state_32 {
> >  	u32 reserved1[62];
> >  	u32 smbase;
> >  	u32 smm_revision;
> > -	u32 reserved2[5];
> > +	u32 reserved2[4];
> > +	u32 int_shadow; /* KVM extension */
> 
> Looking at this with fresh(er) eyes, I agree with Jim: KVM shouldn't add its own
> fields in SMRAM.  There's no need to use vmcb/vmcs memory either, just add fields
> in kvm_vcpu_arch to save/restore the state across SMI/RSM, and then borrow VMX's
> approach of supporting migration by adding flags to do out-of-band migration,
> e.g. KVM_STATE_NESTED_SMM_STI_BLOCKING and KVM_STATE_NESTED_SMM_MOV_SS_BLOCKING.
> 
> 	/* SMM state that's not saved in SMRAM. */
> 	struct {
> 		struct {
> 			u8 interruptibility;
> 		} smm;
> 	} nested;
> 
> That'd finally give us an excuse to move nested_run_pending to common code too :-)
> 
Paolo told me that he wants it to be done this way (save the state in the smram).

My first version of this patch was actually saving the state in kvm internal state,
I personally don't mind that much if to do it this way or another.

But note that I can't use nested state - the int shadow thing has nothing to do with
nesting.

I think that 'struct kvm_vcpu_events' is the right place for this, and in fact it already
has interrupt.shadow (which btw Qemu doesn't migrate...)

My approach was to use upper 4 bits of 'interrupt.shadow' since it is hightly unlikely
that we will ever see more that 16 different interrupt shadows.

It would be a bit more clean to put it into the 'smi' substruct, but we already
have the 'triple_fault' afterwards 

(but I think that this was very recent addition - maybe it is not too late?)

A new 'KVM_VCPUEVENT_VALID_SMM_SHADOW' flag can be added to the struct to indicate the
extra bits if you want.

Best regards,
	Maxim Levitsky

Re: [PATCH v3 13/13] KVM: x86: emulator/smm: preserve interrupt shadow in SMRAM

[Sean Christopherson]

On Thu, Aug 25, 2022, Maxim Levitsky wrote:
> On Wed, 2022-08-24 at 23:50 +0000, Sean Christopherson wrote:
> > On Wed, Aug 03, 2022, Maxim Levitsky wrote:
> > > @@ -518,7 +519,8 @@ struct kvm_smram_state_32 {
> > >  	u32 reserved1[62];
> > >  	u32 smbase;
> > >  	u32 smm_revision;
> > > -	u32 reserved2[5];
> > > +	u32 reserved2[4];
> > > +	u32 int_shadow; /* KVM extension */
> > 
> > Looking at this with fresh(er) eyes, I agree with Jim: KVM shouldn't add its own
> > fields in SMRAM.  There's no need to use vmcb/vmcs memory either, just add fields
> > in kvm_vcpu_arch to save/restore the state across SMI/RSM, and then borrow VMX's
> > approach of supporting migration by adding flags to do out-of-band migration,
> > e.g. KVM_STATE_NESTED_SMM_STI_BLOCKING and KVM_STATE_NESTED_SMM_MOV_SS_BLOCKING.
> > 
> > 	/* SMM state that's not saved in SMRAM. */
> > 	struct {
> > 		struct {
> > 			u8 interruptibility;
> > 		} smm;
> > 	} nested;
> > 
> > That'd finally give us an excuse to move nested_run_pending to common code too :-)
> > 
> Paolo told me that he wants it to be done this way (save the state in the
> smram).

Paolo, what's the motivation for using SMRAM?  I don't see any obvious advantage
for KVM.  QEMU apparently would need to migrate interrupt.shadow, but QEMU should
be doing that anyways, no?

> My first version of this patch was actually saving the state in kvm internal
> state, I personally don't mind that much if to do it this way or another.
> 
> But note that I can't use nested state - the int shadow thing has nothing to
> do with nesting.

Oh, duh.

> I think that 'struct kvm_vcpu_events' is the right place for this, and in fact it already
> has interrupt.shadow (which btw Qemu doesn't migrate...)
> 
> My approach was to use upper 4 bits of 'interrupt.shadow' since it is hightly unlikely
> that we will ever see more that 16 different interrupt shadows.

Heh, unless we ensure STI+MOVSS are mutually exclusive... s/16/4, because
KVM_X86_SHADOW_INT_* are currently treated as masks, not values.

Pedantry aside, using interrupt.shadow definitely seems like the way to go.  We
wouldn't even technically need to use the upper four bits since the bits are KVM
controlled and not hardware-defined, though I agree that using bits 5 and 6 would
give us more flexibility if we ever need to convert the masks to values.

> It would be a bit more clean to put it into the 'smi' substruct, but we already
> have the 'triple_fault' afterwards 
> 
> (but I think that this was very recent addition - maybe it is not too late?)
> 
> A new 'KVM_VCPUEVENT_VALID_SMM_SHADOW' flag can be added to the struct to indicate the
> extra bits if you want.
> 
> Best regards,
> 	Maxim Levitsky
> 
> 
> 

Re: [PATCH v3 00/13] SMM emulation and interrupt shadow fixes

[Thomas Lamprecht]

On 03/08/2022 17:49, Maxim Levitsky wrote:
> This patch series is a result of long debug work to find out why
> sometimes guests with win11 secure boot
> were failing during boot.
> 
> During writing a unit test I found another bug, turns out
> that on rsm emulation, if the rsm instruction was done in real
> or 32 bit mode, KVM would truncate the restored RIP to 32 bit.
> 
> I also refactored the way we write SMRAM so it is easier
> now to understand what is going on.
> 
> The main bug in this series which I fixed is that we
> allowed #SMI to happen during the STI interrupt shadow,
> and we did nothing to both reset it on #SMI handler
> entry and restore it on RSM.
> 
> V3: addressed most of the review feedback from Sean (thanks!)
> 
> Best regards,
> 	Maxim Levitsky
> 
> Maxim Levitsky (13):
>   bug: introduce ASSERT_STRUCT_OFFSET
>   KVM: x86: emulator: em_sysexit should update ctxt->mode
>   KVM: x86: emulator: introduce emulator_recalc_and_set_mode
>   KVM: x86: emulator: update the emulation mode after rsm
>   KVM: x86: emulator: update the emulation mode after CR0 write
>   KVM: x86: emulator/smm: number of GPRs in the SMRAM image depends on
>     the image format
>   KVM: x86: emulator/smm: add structs for KVM's smram layout
>   KVM: x86: emulator/smm: use smram structs in the common code
>   KVM: x86: emulator/smm: use smram struct for 32 bit smram load/restore
>   KVM: x86: emulator/smm: use smram struct for 64 bit smram load/restore
>   KVM: x86: SVM: use smram structs
>   KVM: x86: SVM: don't save SVM state to SMRAM when VM is not long mode
>     capable
>   KVM: x86: emulator/smm: preserve interrupt shadow in SMRAM
> 
>  arch/x86/include/asm/kvm_host.h |  11 +-
>  arch/x86/kvm/emulate.c          | 305 +++++++++++++++++---------------
>  arch/x86/kvm/kvm_emulate.h      | 223 ++++++++++++++++++++++-
>  arch/x86/kvm/svm/svm.c          |  30 ++--
>  arch/x86/kvm/vmx/vmcs12.h       |   5 +-
>  arch/x86/kvm/vmx/vmx.c          |   4 +-
>  arch/x86/kvm/x86.c              | 175 +++++++++---------
>  include/linux/build_bug.h       |   9 +
>  8 files changed, 497 insertions(+), 265 deletions(-)
> 

FWIW, we tested the v2 on 5.19 and backported it to 5.15 with minimal adaption
required (mostly unrelated context change) and now also updated that backport
to the v3 of this patch series.

Our reproducer got fixed with either, but v3 now also avoids triggering logs like:

 Jul 29 04:59:18 mits4 QEMU[2775]: kvm: Could not update PFLASH: Stale file handle
 Jul 29 04:59:18 mits4 QEMU[2775]: kvm: Could not update PFLASH: Stale file handle
 Jul 29 07:15:46 mits4 kernel: kvm: vcpu 1: requested 191999 ns lapic timer period limited to 200000 ns
 Jul 29 11:06:31 mits4 kernel: kvm: vcpu 1: requested 105786 ns lapic timer period limited to 200000 ns

which happened earlier (not sure how deep that correlates with the v2 vs. v3, but
it stuck out, so mentioning for sake of completeness).

For the backport to 5.15 we skipped "KVM: x86: emulator/smm: number of GPRs in
the SMRAM image depends on the image format", as that constant was there yet and
the actual values stayed the same for our case FWICT and adapted to slight context
changes for the others.

So, the approach seems to fix our issue and we are already rolling out a kernel
to users for testing and got positive feedback there too.

With above in mind:

Tested-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

It would be also great to see this backported to still supported upstream stable kernels
from 5.15 onwards, as there the TDP MMU got by default enabled, and that is at least
increasing the chance of our reproducer to trigger dramatically.

thx & cheers
Thomas

Re: [PATCH v3 00/13] SMM emulation and interrupt shadow fixes

[Maxim Levitsky]

On Wed, 2022-08-10 at 14:00 +0200, Thomas Lamprecht wrote:
> On 03/08/2022 17:49, Maxim Levitsky wrote:
> > This patch series is a result of long debug work to find out why
> > sometimes guests with win11 secure boot
> > were failing during boot.
> > 
> > During writing a unit test I found another bug, turns out
> > that on rsm emulation, if the rsm instruction was done in real
> > or 32 bit mode, KVM would truncate the restored RIP to 32 bit.
> > 
> > I also refactored the way we write SMRAM so it is easier
> > now to understand what is going on.
> > 
> > The main bug in this series which I fixed is that we
> > allowed #SMI to happen during the STI interrupt shadow,
> > and we did nothing to both reset it on #SMI handler
> > entry and restore it on RSM.
> > 
> > V3: addressed most of the review feedback from Sean (thanks!)
> > 
> > Best regards,
> >         Maxim Levitsky
> > 
> > Maxim Levitsky (13):
> >   bug: introduce ASSERT_STRUCT_OFFSET
> >   KVM: x86: emulator: em_sysexit should update ctxt->mode
> >   KVM: x86: emulator: introduce emulator_recalc_and_set_mode
> >   KVM: x86: emulator: update the emulation mode after rsm
> >   KVM: x86: emulator: update the emulation mode after CR0 write
> >   KVM: x86: emulator/smm: number of GPRs in the SMRAM image depends on
> >     the image format
> >   KVM: x86: emulator/smm: add structs for KVM's smram layout
> >   KVM: x86: emulator/smm: use smram structs in the common code
> >   KVM: x86: emulator/smm: use smram struct for 32 bit smram load/restore
> >   KVM: x86: emulator/smm: use smram struct for 64 bit smram load/restore
> >   KVM: x86: SVM: use smram structs
> >   KVM: x86: SVM: don't save SVM state to SMRAM when VM is not long mode
> >     capable
> >   KVM: x86: emulator/smm: preserve interrupt shadow in SMRAM
> > 
> >  arch/x86/include/asm/kvm_host.h |  11 +-
> >  arch/x86/kvm/emulate.c          | 305 +++++++++++++++++---------------
> >  arch/x86/kvm/kvm_emulate.h      | 223 ++++++++++++++++++++++-
> >  arch/x86/kvm/svm/svm.c          |  30 ++--
> >  arch/x86/kvm/vmx/vmcs12.h       |   5 +-
> >  arch/x86/kvm/vmx/vmx.c          |   4 +-
> >  arch/x86/kvm/x86.c              | 175 +++++++++---------
> >  include/linux/build_bug.h       |   9 +
> >  8 files changed, 497 insertions(+), 265 deletions(-)
> > 
> 
> FWIW, we tested the v2 on 5.19 and backported it to 5.15 with minimal adaption
> required (mostly unrelated context change) and now also updated that backport
> to the v3 of this patch series.
> 
> Our reproducer got fixed with either, but v3 now also avoids triggering logs like:
> 
>  Jul 29 04:59:18 mits4 QEMU[2775]: kvm: Could not update PFLASH: Stale file handle
>  Jul 29 04:59:18 mits4 QEMU[2775]: kvm: Could not update PFLASH: Stale file handle
>  Jul 29 07:15:46 mits4 kernel: kvm: vcpu 1: requested 191999 ns lapic timer period limited to 200000 ns
>  Jul 29 11:06:31 mits4 kernel: kvm: vcpu 1: requested 105786 ns lapic timer period limited to 200000 ns
> 
> which happened earlier (not sure how deep that correlates with the v2 vs. v3, but
> it stuck out, so mentioning for sake of completeness).

This is likely just a coincidence because V3 should not contain any functional changes vs v2.
(If I remember correctly)

> 
> For the backport to 5.15 we skipped "KVM: x86: emulator/smm: number of GPRs in
> the SMRAM image depends on the image format", as that constant was there yet and
> the actual values stayed the same for our case FWICT and adapted to slight context
> changes for the others.
> 
> So, the approach seems to fix our issue and we are already rolling out a kernel
> to users for testing and got positive feedback there too.
> 
> With above in mind:
> 
> Tested-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

Thank you very much for testing!

> 
> It would be also great to see this backported to still supported upstream stable kernels
> from 5.15 onwards, as there the TDP MMU got by default enabled, and that is at least
> increasing the chance of our reproducer to trigger dramatically.

Best regards,
	Maxim Levitsky

> 
> thx & cheers
> Thomas
>