* [PATCH] kvm: vmx: Stop wasting a page for guest_msrs
@ 2019-12-03 21:08 Jim Mattson
2019-12-03 22:39 ` Liran Alon
2019-12-03 22:59 ` Sean Christopherson
0 siblings, 2 replies; 4+ messages in thread
From: Jim Mattson @ 2019-12-03 21:08 UTC (permalink / raw)
To: kvm; +Cc: Jim Mattson
We will never need more guest_msrs than there are indices in
vmx_msr_index. Thus, at present, the guest_msrs array will not exceed
168 bytes.
Signed-off-by: Jim Mattson <jmattson@google.com>
---
arch/x86/kvm/vmx/vmx.c | 14 ++------------
arch/x86/kvm/vmx/vmx.h | 8 +++++++-
2 files changed, 9 insertions(+), 13 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 1b9ab4166397d..0b3c7524456f1 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -443,7 +443,7 @@ static unsigned long host_idt_base;
* support this emulation, IA32_STAR must always be included in
* vmx_msr_index[], even in i386 builds.
*/
-const u32 vmx_msr_index[] = {
+const u32 vmx_msr_index[NR_GUEST_MSRS] = {
#ifdef CONFIG_X86_64
MSR_SYSCALL_MASK, MSR_LSTAR, MSR_CSTAR,
#endif
@@ -6666,7 +6666,6 @@ static void vmx_free_vcpu(struct kvm_vcpu *vcpu)
free_vpid(vmx->vpid);
nested_vmx_free_vcpu(vcpu);
free_loaded_vmcs(vmx->loaded_vmcs);
- kfree(vmx->guest_msrs);
kvm_vcpu_uninit(vcpu);
kmem_cache_free(x86_fpu_cache, vmx->vcpu.arch.user_fpu);
kmem_cache_free(x86_fpu_cache, vmx->vcpu.arch.guest_fpu);
@@ -6723,13 +6722,6 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
goto uninit_vcpu;
}
- vmx->guest_msrs = kmalloc(PAGE_SIZE, GFP_KERNEL_ACCOUNT);
- BUILD_BUG_ON(ARRAY_SIZE(vmx_msr_index) * sizeof(vmx->guest_msrs[0])
- > PAGE_SIZE);
-
- if (!vmx->guest_msrs)
- goto free_pml;
-
for (i = 0; i < ARRAY_SIZE(vmx_msr_index); ++i) {
u32 index = vmx_msr_index[i];
u32 data_low, data_high;
@@ -6760,7 +6752,7 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
err = alloc_loaded_vmcs(&vmx->vmcs01);
if (err < 0)
- goto free_msrs;
+ goto free_pml;
msr_bitmap = vmx->vmcs01.msr_bitmap;
vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_TSC, MSR_TYPE_R);
@@ -6822,8 +6814,6 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
free_vmcs:
free_loaded_vmcs(vmx->loaded_vmcs);
-free_msrs:
- kfree(vmx->guest_msrs);
free_pml:
vmx_destroy_pml_buffer(vmx);
uninit_vcpu:
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 7c1b978b2df44..08bc24fa59909 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -22,6 +22,12 @@ extern u32 get_umwait_control_msr(void);
#define X2APIC_MSR(r) (APIC_BASE_MSR + ((r) >> 4))
+#ifdef CONFIG_X86_64
+#define NR_GUEST_MSRS 7
+#else
+#define NR_GUEST_MSRS 4
+#endif
+
#define NR_LOADSTORE_MSRS 8
struct vmx_msrs {
@@ -206,7 +212,7 @@ struct vcpu_vmx {
u32 idt_vectoring_info;
ulong rflags;
- struct shared_msr_entry *guest_msrs;
+ struct shared_msr_entry guest_msrs[NR_GUEST_MSRS];
int nmsrs;
int save_nmsrs;
bool guest_msrs_ready;
--
2.24.0.393.g34dc348eaf-goog
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] kvm: vmx: Stop wasting a page for guest_msrs
2019-12-03 21:08 [PATCH] kvm: vmx: Stop wasting a page for guest_msrs Jim Mattson
@ 2019-12-03 22:39 ` Liran Alon
2019-12-03 22:59 ` Sean Christopherson
1 sibling, 0 replies; 4+ messages in thread
From: Liran Alon @ 2019-12-03 22:39 UTC (permalink / raw)
To: Jim Mattson; +Cc: kvm
> On 3 Dec 2019, at 23:08, Jim Mattson <jmattson@google.com> wrote:
>
> We will never need more guest_msrs than there are indices in
> vmx_msr_index. Thus, at present, the guest_msrs array will not exceed
> 168 bytes.
>
> Signed-off-by: Jim Mattson <jmattson@google.com>
Weird that this wasn’t always like this :)
Reviewed-by: Liran Alon <liran.alon@oracle.com>
-Liran
> ---
> arch/x86/kvm/vmx/vmx.c | 14 ++------------
> arch/x86/kvm/vmx/vmx.h | 8 +++++++-
> 2 files changed, 9 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 1b9ab4166397d..0b3c7524456f1 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -443,7 +443,7 @@ static unsigned long host_idt_base;
> * support this emulation, IA32_STAR must always be included in
> * vmx_msr_index[], even in i386 builds.
> */
> -const u32 vmx_msr_index[] = {
> +const u32 vmx_msr_index[NR_GUEST_MSRS] = {
> #ifdef CONFIG_X86_64
> MSR_SYSCALL_MASK, MSR_LSTAR, MSR_CSTAR,
> #endif
> @@ -6666,7 +6666,6 @@ static void vmx_free_vcpu(struct kvm_vcpu *vcpu)
> free_vpid(vmx->vpid);
> nested_vmx_free_vcpu(vcpu);
> free_loaded_vmcs(vmx->loaded_vmcs);
> - kfree(vmx->guest_msrs);
> kvm_vcpu_uninit(vcpu);
> kmem_cache_free(x86_fpu_cache, vmx->vcpu.arch.user_fpu);
> kmem_cache_free(x86_fpu_cache, vmx->vcpu.arch.guest_fpu);
> @@ -6723,13 +6722,6 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
> goto uninit_vcpu;
> }
>
> - vmx->guest_msrs = kmalloc(PAGE_SIZE, GFP_KERNEL_ACCOUNT);
> - BUILD_BUG_ON(ARRAY_SIZE(vmx_msr_index) * sizeof(vmx->guest_msrs[0])
> - > PAGE_SIZE);
> -
> - if (!vmx->guest_msrs)
> - goto free_pml;
> -
> for (i = 0; i < ARRAY_SIZE(vmx_msr_index); ++i) {
> u32 index = vmx_msr_index[i];
> u32 data_low, data_high;
> @@ -6760,7 +6752,7 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
>
> err = alloc_loaded_vmcs(&vmx->vmcs01);
> if (err < 0)
> - goto free_msrs;
> + goto free_pml;
>
> msr_bitmap = vmx->vmcs01.msr_bitmap;
> vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_TSC, MSR_TYPE_R);
> @@ -6822,8 +6814,6 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
>
> free_vmcs:
> free_loaded_vmcs(vmx->loaded_vmcs);
> -free_msrs:
> - kfree(vmx->guest_msrs);
> free_pml:
> vmx_destroy_pml_buffer(vmx);
> uninit_vcpu:
> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
> index 7c1b978b2df44..08bc24fa59909 100644
> --- a/arch/x86/kvm/vmx/vmx.h
> +++ b/arch/x86/kvm/vmx/vmx.h
> @@ -22,6 +22,12 @@ extern u32 get_umwait_control_msr(void);
>
> #define X2APIC_MSR(r) (APIC_BASE_MSR + ((r) >> 4))
>
> +#ifdef CONFIG_X86_64
> +#define NR_GUEST_MSRS 7
> +#else
> +#define NR_GUEST_MSRS 4
> +#endif
> +
> #define NR_LOADSTORE_MSRS 8
>
> struct vmx_msrs {
> @@ -206,7 +212,7 @@ struct vcpu_vmx {
> u32 idt_vectoring_info;
> ulong rflags;
>
> - struct shared_msr_entry *guest_msrs;
> + struct shared_msr_entry guest_msrs[NR_GUEST_MSRS];
> int nmsrs;
> int save_nmsrs;
> bool guest_msrs_ready;
> --
> 2.24.0.393.g34dc348eaf-goog
>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] kvm: vmx: Stop wasting a page for guest_msrs
2019-12-03 21:08 [PATCH] kvm: vmx: Stop wasting a page for guest_msrs Jim Mattson
2019-12-03 22:39 ` Liran Alon
@ 2019-12-03 22:59 ` Sean Christopherson
2019-12-03 23:24 ` Jim Mattson
1 sibling, 1 reply; 4+ messages in thread
From: Sean Christopherson @ 2019-12-03 22:59 UTC (permalink / raw)
To: Jim Mattson; +Cc: kvm
On Tue, Dec 03, 2019 at 01:08:25PM -0800, Jim Mattson wrote:
> We will never need more guest_msrs than there are indices in
> vmx_msr_index. Thus, at present, the guest_msrs array will not exceed
> 168 bytes.
>
> Signed-off-by: Jim Mattson <jmattson@google.com>
> ---
> arch/x86/kvm/vmx/vmx.c | 14 ++------------
> arch/x86/kvm/vmx/vmx.h | 8 +++++++-
> 2 files changed, 9 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 1b9ab4166397d..0b3c7524456f1 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -443,7 +443,7 @@ static unsigned long host_idt_base;
> * support this emulation, IA32_STAR must always be included in
> * vmx_msr_index[], even in i386 builds.
> */
> -const u32 vmx_msr_index[] = {
> +const u32 vmx_msr_index[NR_GUEST_MSRS] = {
What if we keep this as is and add
BUILD_BUG_ON(ARRAY_SIZE(vmx_msr_index) != NR_SHARED_MSRS);
in setup_msrs()? That way the build will fail if someone adds an MSR but
forgets to update the #define. With this change, gcc only spits out a
warning if the number of elements exceeds the size of the array and
presumably drops the extra elements on the floor.
> #ifdef CONFIG_X86_64
> MSR_SYSCALL_MASK, MSR_LSTAR, MSR_CSTAR,
> #endif
> @@ -6666,7 +6666,6 @@ static void vmx_free_vcpu(struct kvm_vcpu *vcpu)
> free_vpid(vmx->vpid);
> nested_vmx_free_vcpu(vcpu);
> free_loaded_vmcs(vmx->loaded_vmcs);
> - kfree(vmx->guest_msrs);
> kvm_vcpu_uninit(vcpu);
> kmem_cache_free(x86_fpu_cache, vmx->vcpu.arch.user_fpu);
> kmem_cache_free(x86_fpu_cache, vmx->vcpu.arch.guest_fpu);
> @@ -6723,13 +6722,6 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
> goto uninit_vcpu;
> }
>
> - vmx->guest_msrs = kmalloc(PAGE_SIZE, GFP_KERNEL_ACCOUNT);
> - BUILD_BUG_ON(ARRAY_SIZE(vmx_msr_index) * sizeof(vmx->guest_msrs[0])
> - > PAGE_SIZE);
> -
> - if (!vmx->guest_msrs)
> - goto free_pml;
> -
> for (i = 0; i < ARRAY_SIZE(vmx_msr_index); ++i) {
> u32 index = vmx_msr_index[i];
> u32 data_low, data_high;
> @@ -6760,7 +6752,7 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
>
> err = alloc_loaded_vmcs(&vmx->vmcs01);
> if (err < 0)
> - goto free_msrs;
> + goto free_pml;
>
> msr_bitmap = vmx->vmcs01.msr_bitmap;
> vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_TSC, MSR_TYPE_R);
> @@ -6822,8 +6814,6 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
>
> free_vmcs:
> free_loaded_vmcs(vmx->loaded_vmcs);
> -free_msrs:
> - kfree(vmx->guest_msrs);
> free_pml:
> vmx_destroy_pml_buffer(vmx);
> uninit_vcpu:
> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
> index 7c1b978b2df44..08bc24fa59909 100644
> --- a/arch/x86/kvm/vmx/vmx.h
> +++ b/arch/x86/kvm/vmx/vmx.h
> @@ -22,6 +22,12 @@ extern u32 get_umwait_control_msr(void);
>
> #define X2APIC_MSR(r) (APIC_BASE_MSR + ((r) >> 4))
>
> +#ifdef CONFIG_X86_64
> +#define NR_GUEST_MSRS 7
> +#else
> +#define NR_GUEST_MSRS 4
> +#endif
As much as I hate the "shared msrs" terminology, "guest msrs" is even
more confusing and misleading. NR_SHARED_MSRS?
> +
> #define NR_LOADSTORE_MSRS 8
>
> struct vmx_msrs {
> @@ -206,7 +212,7 @@ struct vcpu_vmx {
> u32 idt_vectoring_info;
> ulong rflags;
>
> - struct shared_msr_entry *guest_msrs;
> + struct shared_msr_entry guest_msrs[NR_GUEST_MSRS];
> int nmsrs;
> int save_nmsrs;
> bool guest_msrs_ready;
> --
> 2.24.0.393.g34dc348eaf-goog
>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] kvm: vmx: Stop wasting a page for guest_msrs
2019-12-03 22:59 ` Sean Christopherson
@ 2019-12-03 23:24 ` Jim Mattson
0 siblings, 0 replies; 4+ messages in thread
From: Jim Mattson @ 2019-12-03 23:24 UTC (permalink / raw)
To: Sean Christopherson; +Cc: kvm list
On Tue, Dec 3, 2019 at 2:59 PM Sean Christopherson
<sean.j.christopherson@intel.com> wrote:
>
> On Tue, Dec 03, 2019 at 01:08:25PM -0800, Jim Mattson wrote:
> > We will never need more guest_msrs than there are indices in
> > vmx_msr_index. Thus, at present, the guest_msrs array will not exceed
> > 168 bytes.
> >
> > Signed-off-by: Jim Mattson <jmattson@google.com>
> > ---
> > arch/x86/kvm/vmx/vmx.c | 14 ++------------
> > arch/x86/kvm/vmx/vmx.h | 8 +++++++-
> > 2 files changed, 9 insertions(+), 13 deletions(-)
> >
> > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> > index 1b9ab4166397d..0b3c7524456f1 100644
> > --- a/arch/x86/kvm/vmx/vmx.c
> > +++ b/arch/x86/kvm/vmx/vmx.c
> > @@ -443,7 +443,7 @@ static unsigned long host_idt_base;
> > * support this emulation, IA32_STAR must always be included in
> > * vmx_msr_index[], even in i386 builds.
> > */
> > -const u32 vmx_msr_index[] = {
> > +const u32 vmx_msr_index[NR_GUEST_MSRS] = {
>
> What if we keep this as is and add
>
> BUILD_BUG_ON(ARRAY_SIZE(vmx_msr_index) != NR_SHARED_MSRS);
>
> in setup_msrs()? That way the build will fail if someone adds an MSR but
> forgets to update the #define. With this change, gcc only spits out a
> warning if the number of elements exceeds the size of the array and
> presumably drops the extra elements on the floor.
Instead of setup_msrs(), what if I add that BUILD_BUG_ON() in
vmx_create_vcpu(), where I'm getting rid of the old BUILD_BUG_ON()
regarding ARRAY_SIZE(vmx_msr_index)?
> > #ifdef CONFIG_X86_64
> > MSR_SYSCALL_MASK, MSR_LSTAR, MSR_CSTAR,
> > #endif
> > @@ -6666,7 +6666,6 @@ static void vmx_free_vcpu(struct kvm_vcpu *vcpu)
> > free_vpid(vmx->vpid);
> > nested_vmx_free_vcpu(vcpu);
> > free_loaded_vmcs(vmx->loaded_vmcs);
> > - kfree(vmx->guest_msrs);
> > kvm_vcpu_uninit(vcpu);
> > kmem_cache_free(x86_fpu_cache, vmx->vcpu.arch.user_fpu);
> > kmem_cache_free(x86_fpu_cache, vmx->vcpu.arch.guest_fpu);
> > @@ -6723,13 +6722,6 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
> > goto uninit_vcpu;
> > }
> >
> > - vmx->guest_msrs = kmalloc(PAGE_SIZE, GFP_KERNEL_ACCOUNT);
> > - BUILD_BUG_ON(ARRAY_SIZE(vmx_msr_index) * sizeof(vmx->guest_msrs[0])
> > - > PAGE_SIZE);
> > -
> > - if (!vmx->guest_msrs)
> > - goto free_pml;
> > -
> > for (i = 0; i < ARRAY_SIZE(vmx_msr_index); ++i) {
> > u32 index = vmx_msr_index[i];
> > u32 data_low, data_high;
> > @@ -6760,7 +6752,7 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
> >
> > err = alloc_loaded_vmcs(&vmx->vmcs01);
> > if (err < 0)
> > - goto free_msrs;
> > + goto free_pml;
> >
> > msr_bitmap = vmx->vmcs01.msr_bitmap;
> > vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_TSC, MSR_TYPE_R);
> > @@ -6822,8 +6814,6 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
> >
> > free_vmcs:
> > free_loaded_vmcs(vmx->loaded_vmcs);
> > -free_msrs:
> > - kfree(vmx->guest_msrs);
> > free_pml:
> > vmx_destroy_pml_buffer(vmx);
> > uninit_vcpu:
> > diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
> > index 7c1b978b2df44..08bc24fa59909 100644
> > --- a/arch/x86/kvm/vmx/vmx.h
> > +++ b/arch/x86/kvm/vmx/vmx.h
> > @@ -22,6 +22,12 @@ extern u32 get_umwait_control_msr(void);
> >
> > #define X2APIC_MSR(r) (APIC_BASE_MSR + ((r) >> 4))
> >
> > +#ifdef CONFIG_X86_64
> > +#define NR_GUEST_MSRS 7
> > +#else
> > +#define NR_GUEST_MSRS 4
> > +#endif
>
> As much as I hate the "shared msrs" terminology, "guest msrs" is even
> more confusing and misleading. NR_SHARED_MSRS?
>
> > +
> > #define NR_LOADSTORE_MSRS 8
> >
> > struct vmx_msrs {
> > @@ -206,7 +212,7 @@ struct vcpu_vmx {
> > u32 idt_vectoring_info;
> > ulong rflags;
> >
> > - struct shared_msr_entry *guest_msrs;
> > + struct shared_msr_entry guest_msrs[NR_GUEST_MSRS];
> > int nmsrs;
> > int save_nmsrs;
> > bool guest_msrs_ready;
> > --
> > 2.24.0.393.g34dc348eaf-goog
> >
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2019-12-03 23:24 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-12-03 21:08 [PATCH] kvm: vmx: Stop wasting a page for guest_msrs Jim Mattson
2019-12-03 22:39 ` Liran Alon
2019-12-03 22:59 ` Sean Christopherson
2019-12-03 23:24 ` Jim Mattson
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