* [PATCH] KVM: x86: Restrict get_mt_mask() to a u8, use KVM_X86_OP_OPTIONAL_RET0
@ 2022-07-14 15:37 Sean Christopherson
2022-07-14 15:43 ` Paolo Bonzini
0 siblings, 1 reply; 2+ messages in thread
From: Sean Christopherson @ 2022-07-14 15:37 UTC (permalink / raw)
To: Sean Christopherson, Paolo Bonzini; +Cc: kvm, linux-kernel
Restrict get_mt_mask() to a u8 and reintroduce using a RET0 static_call
for the SVM implementation. EPT stores the memtype information in the
lower 8 bits (bits 6:3 to be precise), and even returns a shifted u8
without an explicit cast to a larger type; there's no need to return a
full u64.
Note, RET0 doesn't play nice with a u64 return on 32-bit kernels, see
commit bf07be36cd88 ("KVM: x86: do not use KVM_X86_OP_OPTIONAL_RET0 for
get_mt_mask").
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/include/asm/kvm-x86-ops.h | 2 +-
arch/x86/include/asm/kvm_host.h | 2 +-
arch/x86/kvm/svm/svm.c | 6 ------
arch/x86/kvm/vmx/vmx.c | 2 +-
4 files changed, 3 insertions(+), 9 deletions(-)
diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index 6f2f1affbb78..51f777071584 100644
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -88,7 +88,7 @@ KVM_X86_OP(deliver_interrupt)
KVM_X86_OP_OPTIONAL(sync_pir_to_irr)
KVM_X86_OP_OPTIONAL_RET0(set_tss_addr)
KVM_X86_OP_OPTIONAL_RET0(set_identity_map_addr)
-KVM_X86_OP(get_mt_mask)
+KVM_X86_OP_OPTIONAL_RET0(get_mt_mask)
KVM_X86_OP(load_mmu_pgd)
KVM_X86_OP(has_wbinvd_exit)
KVM_X86_OP(get_l2_tsc_offset)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index de5a149d0971..fa4b2392fba0 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1546,7 +1546,7 @@ struct kvm_x86_ops {
int (*sync_pir_to_irr)(struct kvm_vcpu *vcpu);
int (*set_tss_addr)(struct kvm *kvm, unsigned int addr);
int (*set_identity_map_addr)(struct kvm *kvm, u64 ident_addr);
- u64 (*get_mt_mask)(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio);
+ u8 (*get_mt_mask)(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio);
void (*load_mmu_pgd)(struct kvm_vcpu *vcpu, hpa_t root_hpa,
int root_level);
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 37ce061dfc76..19af6dacfc5b 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4158,11 +4158,6 @@ static bool svm_has_emulated_msr(struct kvm *kvm, u32 index)
return true;
}
-static u64 svm_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
-{
- return 0;
-}
-
static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
{
struct vcpu_svm *svm = to_svm(vcpu);
@@ -4814,7 +4809,6 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
.check_apicv_inhibit_reasons = avic_check_apicv_inhibit_reasons,
.apicv_post_state_restore = avic_apicv_post_state_restore,
- .get_mt_mask = svm_get_mt_mask,
.get_exit_info = svm_get_exit_info,
.vcpu_after_set_cpuid = svm_vcpu_after_set_cpuid,
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index c30115b9cb33..c895a3b6824d 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7352,7 +7352,7 @@ static int __init vmx_check_processor_compat(void)
return 0;
}
-static u64 vmx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
+static u8 vmx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
{
u8 cache;
base-commit: b9b71f43683ae9d76b0989249607bbe8c9eb6c5c
--
2.37.0.144.g8ac04bfd2-goog
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] KVM: x86: Restrict get_mt_mask() to a u8, use KVM_X86_OP_OPTIONAL_RET0
2022-07-14 15:37 [PATCH] KVM: x86: Restrict get_mt_mask() to a u8, use KVM_X86_OP_OPTIONAL_RET0 Sean Christopherson
@ 2022-07-14 15:43 ` Paolo Bonzini
0 siblings, 0 replies; 2+ messages in thread
From: Paolo Bonzini @ 2022-07-14 15:43 UTC (permalink / raw)
To: Sean Christopherson; +Cc: kvm, linux-kernel
On 7/14/22 17:37, Sean Christopherson wrote:
> Restrict get_mt_mask() to a u8 and reintroduce using a RET0 static_call
> for the SVM implementation. EPT stores the memtype information in the
> lower 8 bits (bits 6:3 to be precise), and even returns a shifted u8
> without an explicit cast to a larger type; there's no need to return a
> full u64.
>
> Note, RET0 doesn't play nice with a u64 return on 32-bit kernels, see
> commit bf07be36cd88 ("KVM: x86: do not use KVM_X86_OP_OPTIONAL_RET0 for
> get_mt_mask").
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
Doh, that's obvious. Queued, thanks.
Paolo
> ---
> arch/x86/include/asm/kvm-x86-ops.h | 2 +-
> arch/x86/include/asm/kvm_host.h | 2 +-
> arch/x86/kvm/svm/svm.c | 6 ------
> arch/x86/kvm/vmx/vmx.c | 2 +-
> 4 files changed, 3 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
> index 6f2f1affbb78..51f777071584 100644
> --- a/arch/x86/include/asm/kvm-x86-ops.h
> +++ b/arch/x86/include/asm/kvm-x86-ops.h
> @@ -88,7 +88,7 @@ KVM_X86_OP(deliver_interrupt)
> KVM_X86_OP_OPTIONAL(sync_pir_to_irr)
> KVM_X86_OP_OPTIONAL_RET0(set_tss_addr)
> KVM_X86_OP_OPTIONAL_RET0(set_identity_map_addr)
> -KVM_X86_OP(get_mt_mask)
> +KVM_X86_OP_OPTIONAL_RET0(get_mt_mask)
> KVM_X86_OP(load_mmu_pgd)
> KVM_X86_OP(has_wbinvd_exit)
> KVM_X86_OP(get_l2_tsc_offset)
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index de5a149d0971..fa4b2392fba0 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1546,7 +1546,7 @@ struct kvm_x86_ops {
> int (*sync_pir_to_irr)(struct kvm_vcpu *vcpu);
> int (*set_tss_addr)(struct kvm *kvm, unsigned int addr);
> int (*set_identity_map_addr)(struct kvm *kvm, u64 ident_addr);
> - u64 (*get_mt_mask)(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio);
> + u8 (*get_mt_mask)(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio);
>
> void (*load_mmu_pgd)(struct kvm_vcpu *vcpu, hpa_t root_hpa,
> int root_level);
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 37ce061dfc76..19af6dacfc5b 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -4158,11 +4158,6 @@ static bool svm_has_emulated_msr(struct kvm *kvm, u32 index)
> return true;
> }
>
> -static u64 svm_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
> -{
> - return 0;
> -}
> -
> static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
> {
> struct vcpu_svm *svm = to_svm(vcpu);
> @@ -4814,7 +4809,6 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
> .check_apicv_inhibit_reasons = avic_check_apicv_inhibit_reasons,
> .apicv_post_state_restore = avic_apicv_post_state_restore,
>
> - .get_mt_mask = svm_get_mt_mask,
> .get_exit_info = svm_get_exit_info,
>
> .vcpu_after_set_cpuid = svm_vcpu_after_set_cpuid,
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index c30115b9cb33..c895a3b6824d 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7352,7 +7352,7 @@ static int __init vmx_check_processor_compat(void)
> return 0;
> }
>
> -static u64 vmx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
> +static u8 vmx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
> {
> u8 cache;
>
>
> base-commit: b9b71f43683ae9d76b0989249607bbe8c9eb6c5c
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2022-07-14 15:37 [PATCH] KVM: x86: Restrict get_mt_mask() to a u8, use KVM_X86_OP_OPTIONAL_RET0 Sean Christopherson
2022-07-14 15:43 ` Paolo Bonzini
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