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From: Joerg Roedel <joro@8bytes.org>
To: x86@kernel.org
Cc: Joerg Roedel <joro@8bytes.org>, Joerg Roedel <jroedel@suse.de>,
	hpa@zytor.com, Andy Lutomirski <luto@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Jiri Slaby <jslaby@suse.cz>,
	Dan Williams <dan.j.williams@intel.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Juergen Gross <jgross@suse.com>,
	Kees Cook <keescook@chromium.org>,
	David Rientjes <rientjes@google.com>,
	Cfir Cohen <cfir@google.com>, Erdem Aktas <erdemaktas@google.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Mike Stunes <mstunes@vmware.com>,
	Sean Christopherson <seanjc@google.com>,
	Martin Radev <martin.b.radev@gmail.com>,
	Arvind Sankar <nivedita@alum.mit.edu>,
	linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org,
	kvm@vger.kernel.org, virtualization@lists.linux-foundation.org
Subject: [PATCH v4 2/6] x86/sev-es: Disable IRQs while GHCB is active
Date: Thu, 10 Jun 2021 11:11:37 +0200	[thread overview]
Message-ID: <20210610091141.30322-3-joro@8bytes.org> (raw)
In-Reply-To: <20210610091141.30322-1-joro@8bytes.org>

From: Joerg Roedel <jroedel@suse.de>

The #VC handler only cares about IRQs being disabled while the GHCB is
active, as it must not be interrupted by something which could cause
another #VC while it holds the GHCB (NMI is the exception for which the
backup GHCB is there).

Make sure nothing interrupts the code path while the GHCB is active by
disabling IRQs in sev_es_get_ghcb() and restoring the previous irq state
in sev_es_put_ghcb().

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 arch/x86/kernel/sev.c | 39 +++++++++++++++++++++++++--------------
 1 file changed, 25 insertions(+), 14 deletions(-)

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 4fd997bbf059..2a922d1b03c8 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -192,14 +192,23 @@ void noinstr __sev_es_ist_exit(void)
 	this_cpu_write(cpu_tss_rw.x86_tss.ist[IST_INDEX_VC], *(unsigned long *)ist);
 }
 
-static __always_inline struct ghcb *sev_es_get_ghcb(struct ghcb_state *state)
+static __always_inline struct ghcb *sev_es_get_ghcb(struct ghcb_state *state,
+						    unsigned long *flags)
 {
 	struct sev_es_runtime_data *data;
 	struct ghcb *ghcb;
 
+	/*
+	 * Nothing shall interrupt this code path while holding the per-cpu
+	 * GHCB. The backup GHCB is only for NMIs interrupting this path.
+	 */
+	local_irq_save(*flags);
+
 	data = this_cpu_read(runtime_data);
 	ghcb = &data->ghcb_page;
 
+
+
 	if (unlikely(data->ghcb_active)) {
 		/* GHCB is already in use - save its contents */
 
@@ -479,7 +488,8 @@ static enum es_result vc_slow_virt_to_phys(struct ghcb *ghcb, struct es_em_ctxt
 /* Include code shared with pre-decompression boot stage */
 #include "sev-shared.c"
 
-static __always_inline void sev_es_put_ghcb(struct ghcb_state *state)
+static __always_inline void sev_es_put_ghcb(struct ghcb_state *state,
+					    unsigned long flags)
 {
 	struct sev_es_runtime_data *data;
 	struct ghcb *ghcb;
@@ -500,14 +510,17 @@ static __always_inline void sev_es_put_ghcb(struct ghcb_state *state)
 		vc_ghcb_invalidate(ghcb);
 		data->ghcb_active = false;
 	}
+
+	local_irq_restore(flags);
 }
 
 void noinstr __sev_es_nmi_complete(void)
 {
 	struct ghcb_state state;
+	unsigned long flags;
 	struct ghcb *ghcb;
 
-	ghcb = sev_es_get_ghcb(&state);
+	ghcb = sev_es_get_ghcb(&state, &flags);
 
 	vc_ghcb_invalidate(ghcb);
 	ghcb_set_sw_exit_code(ghcb, SVM_VMGEXIT_NMI_COMPLETE);
@@ -517,7 +530,7 @@ void noinstr __sev_es_nmi_complete(void)
 	sev_es_wr_ghcb_msr(__pa_nodebug(ghcb));
 	VMGEXIT();
 
-	sev_es_put_ghcb(&state);
+	sev_es_put_ghcb(&state, flags);
 }
 
 static u64 get_jump_table_addr(void)
@@ -527,9 +540,7 @@ static u64 get_jump_table_addr(void)
 	struct ghcb *ghcb;
 	u64 ret = 0;
 
-	local_irq_save(flags);
-
-	ghcb = sev_es_get_ghcb(&state);
+	ghcb = sev_es_get_ghcb(&state, &flags);
 
 	vc_ghcb_invalidate(ghcb);
 	ghcb_set_sw_exit_code(ghcb, SVM_VMGEXIT_AP_JUMP_TABLE);
@@ -543,9 +554,7 @@ static u64 get_jump_table_addr(void)
 	    ghcb_sw_exit_info_2_is_valid(ghcb))
 		ret = ghcb->save.sw_exit_info_2;
 
-	sev_es_put_ghcb(&state);
-
-	local_irq_restore(flags);
+	sev_es_put_ghcb(&state, flags);
 
 	return ret;
 }
@@ -666,9 +675,10 @@ static bool __init sev_es_setup_ghcb(void)
 static void sev_es_ap_hlt_loop(void)
 {
 	struct ghcb_state state;
+	unsigned long flags;
 	struct ghcb *ghcb;
 
-	ghcb = sev_es_get_ghcb(&state);
+	ghcb = sev_es_get_ghcb(&state, &flags);
 
 	while (true) {
 		vc_ghcb_invalidate(ghcb);
@@ -685,7 +695,7 @@ static void sev_es_ap_hlt_loop(void)
 			break;
 	}
 
-	sev_es_put_ghcb(&state);
+	sev_es_put_ghcb(&state, flags);
 }
 
 /*
@@ -1333,6 +1343,7 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication)
 	struct ghcb_state state;
 	struct es_em_ctxt ctxt;
 	enum es_result result;
+	unsigned long flags;
 	struct ghcb *ghcb;
 
 	/*
@@ -1353,7 +1364,7 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication)
 	 * keep the IRQs disabled to protect us against concurrent TLB flushes.
 	 */
 
-	ghcb = sev_es_get_ghcb(&state);
+	ghcb = sev_es_get_ghcb(&state, &flags);
 
 	vc_ghcb_invalidate(ghcb);
 	result = vc_init_em_ctxt(&ctxt, regs, error_code);
@@ -1361,7 +1372,7 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication)
 	if (result == ES_OK)
 		result = vc_handle_exitcode(&ctxt, ghcb, error_code);
 
-	sev_es_put_ghcb(&state);
+	sev_es_put_ghcb(&state, flags);
 
 	/* Done - now check the result */
 	switch (result) {
-- 
2.31.1


WARNING: multiple messages have this Message-ID
From: Joerg Roedel <joro@8bytes.org>
To: x86@kernel.org
Cc: kvm@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	virtualization@lists.linux-foundation.org,
	Arvind Sankar <nivedita@alum.mit.edu>,
	hpa@zytor.com, Jiri Slaby <jslaby@suse.cz>,
	Joerg Roedel <joro@8bytes.org>,
	David Rientjes <rientjes@google.com>,
	Martin Radev <martin.b.radev@gmail.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Joerg Roedel <jroedel@suse.de>, Kees Cook <keescook@chromium.org>,
	Cfir Cohen <cfir@google.com>,
	linux-coco@lists.linux.dev, Andy Lutomirski <luto@kernel.org>,
	Dan Williams <dan.j.williams@intel.com>,
	Juergen Gross <jgross@suse.com>, Mike Stunes <mstunes@vmware.com>,
	Sean Christopherson <seanjc@google.com>,
	linux-kernel@vger.kernel.org,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Erdem Aktas <erdemaktas@google.com>
Subject: [PATCH v4 2/6] x86/sev-es: Disable IRQs while GHCB is active
Date: Thu, 10 Jun 2021 11:11:37 +0200	[thread overview]
Message-ID: <20210610091141.30322-3-joro@8bytes.org> (raw)
In-Reply-To: <20210610091141.30322-1-joro@8bytes.org>

From: Joerg Roedel <jroedel@suse.de>

The #VC handler only cares about IRQs being disabled while the GHCB is
active, as it must not be interrupted by something which could cause
another #VC while it holds the GHCB (NMI is the exception for which the
backup GHCB is there).

Make sure nothing interrupts the code path while the GHCB is active by
disabling IRQs in sev_es_get_ghcb() and restoring the previous irq state
in sev_es_put_ghcb().

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 arch/x86/kernel/sev.c | 39 +++++++++++++++++++++++++--------------
 1 file changed, 25 insertions(+), 14 deletions(-)

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 4fd997bbf059..2a922d1b03c8 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -192,14 +192,23 @@ void noinstr __sev_es_ist_exit(void)
 	this_cpu_write(cpu_tss_rw.x86_tss.ist[IST_INDEX_VC], *(unsigned long *)ist);
 }
 
-static __always_inline struct ghcb *sev_es_get_ghcb(struct ghcb_state *state)
+static __always_inline struct ghcb *sev_es_get_ghcb(struct ghcb_state *state,
+						    unsigned long *flags)
 {
 	struct sev_es_runtime_data *data;
 	struct ghcb *ghcb;
 
+	/*
+	 * Nothing shall interrupt this code path while holding the per-cpu
+	 * GHCB. The backup GHCB is only for NMIs interrupting this path.
+	 */
+	local_irq_save(*flags);
+
 	data = this_cpu_read(runtime_data);
 	ghcb = &data->ghcb_page;
 
+
+
 	if (unlikely(data->ghcb_active)) {
 		/* GHCB is already in use - save its contents */
 
@@ -479,7 +488,8 @@ static enum es_result vc_slow_virt_to_phys(struct ghcb *ghcb, struct es_em_ctxt
 /* Include code shared with pre-decompression boot stage */
 #include "sev-shared.c"
 
-static __always_inline void sev_es_put_ghcb(struct ghcb_state *state)
+static __always_inline void sev_es_put_ghcb(struct ghcb_state *state,
+					    unsigned long flags)
 {
 	struct sev_es_runtime_data *data;
 	struct ghcb *ghcb;
@@ -500,14 +510,17 @@ static __always_inline void sev_es_put_ghcb(struct ghcb_state *state)
 		vc_ghcb_invalidate(ghcb);
 		data->ghcb_active = false;
 	}
+
+	local_irq_restore(flags);
 }
 
 void noinstr __sev_es_nmi_complete(void)
 {
 	struct ghcb_state state;
+	unsigned long flags;
 	struct ghcb *ghcb;
 
-	ghcb = sev_es_get_ghcb(&state);
+	ghcb = sev_es_get_ghcb(&state, &flags);
 
 	vc_ghcb_invalidate(ghcb);
 	ghcb_set_sw_exit_code(ghcb, SVM_VMGEXIT_NMI_COMPLETE);
@@ -517,7 +530,7 @@ void noinstr __sev_es_nmi_complete(void)
 	sev_es_wr_ghcb_msr(__pa_nodebug(ghcb));
 	VMGEXIT();
 
-	sev_es_put_ghcb(&state);
+	sev_es_put_ghcb(&state, flags);
 }
 
 static u64 get_jump_table_addr(void)
@@ -527,9 +540,7 @@ static u64 get_jump_table_addr(void)
 	struct ghcb *ghcb;
 	u64 ret = 0;
 
-	local_irq_save(flags);
-
-	ghcb = sev_es_get_ghcb(&state);
+	ghcb = sev_es_get_ghcb(&state, &flags);
 
 	vc_ghcb_invalidate(ghcb);
 	ghcb_set_sw_exit_code(ghcb, SVM_VMGEXIT_AP_JUMP_TABLE);
@@ -543,9 +554,7 @@ static u64 get_jump_table_addr(void)
 	    ghcb_sw_exit_info_2_is_valid(ghcb))
 		ret = ghcb->save.sw_exit_info_2;
 
-	sev_es_put_ghcb(&state);
-
-	local_irq_restore(flags);
+	sev_es_put_ghcb(&state, flags);
 
 	return ret;
 }
@@ -666,9 +675,10 @@ static bool __init sev_es_setup_ghcb(void)
 static void sev_es_ap_hlt_loop(void)
 {
 	struct ghcb_state state;
+	unsigned long flags;
 	struct ghcb *ghcb;
 
-	ghcb = sev_es_get_ghcb(&state);
+	ghcb = sev_es_get_ghcb(&state, &flags);
 
 	while (true) {
 		vc_ghcb_invalidate(ghcb);
@@ -685,7 +695,7 @@ static void sev_es_ap_hlt_loop(void)
 			break;
 	}
 
-	sev_es_put_ghcb(&state);
+	sev_es_put_ghcb(&state, flags);
 }
 
 /*
@@ -1333,6 +1343,7 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication)
 	struct ghcb_state state;
 	struct es_em_ctxt ctxt;
 	enum es_result result;
+	unsigned long flags;
 	struct ghcb *ghcb;
 
 	/*
@@ -1353,7 +1364,7 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication)
 	 * keep the IRQs disabled to protect us against concurrent TLB flushes.
 	 */
 
-	ghcb = sev_es_get_ghcb(&state);
+	ghcb = sev_es_get_ghcb(&state, &flags);
 
 	vc_ghcb_invalidate(ghcb);
 	result = vc_init_em_ctxt(&ctxt, regs, error_code);
@@ -1361,7 +1372,7 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication)
 	if (result == ES_OK)
 		result = vc_handle_exitcode(&ctxt, ghcb, error_code);
 
-	sev_es_put_ghcb(&state);
+	sev_es_put_ghcb(&state, flags);
 
 	/* Done - now check the result */
 	switch (result) {
-- 
2.31.1

_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization

  parent reply	other threads:[~2021-06-10  9:12 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-10  9:11 [PATCH v4 0/6] x86/sev-es: Fixes for SEV-ES Guest Support Joerg Roedel
2021-06-10  9:11 ` [PATCH v4 1/6] x86/sev-es: Fix error message in runtime #VC handler Joerg Roedel
2021-06-10  9:11 ` Joerg Roedel [this message]
2021-06-11 14:05   ` [PATCH v4 2/6] x86/sev-es: Disable IRQs while GHCB is active Borislav Petkov
2021-06-11 14:20     ` Joerg Roedel
2021-06-11 14:34       ` Borislav Petkov
2021-06-10  9:11 ` [PATCH v4 3/6] x86/sev-es: Split up runtime #VC handler for correct state tracking Joerg Roedel
2021-06-10 10:19   ` Peter Zijlstra
2021-06-10 11:30     ` Joerg Roedel
2021-06-10  9:11 ` [PATCH v4 4/6] x86/insn-eval: Make 0 a valid RIP for insn_get_effective_ip() Joerg Roedel
2021-06-10  9:11 ` [PATCH v4 5/6] x86/insn: Extend error reporting from insn_fetch_from_user[_inatomic]() Joerg Roedel
2021-06-10  9:11 ` [PATCH v4 6/6] x86/sev-es: Propagate #GP if getting linear instruction address failed Joerg Roedel

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