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* [PATCH v2 0/2] KVM: x86: Replace magic number with readable macro
@ 2022-03-29  3:01 SU Hang
  2022-03-29  3:01 ` [PATCH v2 1/2] KVM: VMX: replace 0x180 with EPT_VIOLATION_* definition SU Hang
                   ` (2 more replies)
  0 siblings, 3 replies; 8+ messages in thread
From: SU Hang @ 2022-03-29  3:01 UTC (permalink / raw)
  To: seanjc, kvm
  Cc: Lai Jiangshan, SU Hang, Thomas Gleixner, Ingo Molnar,
	Borislav Petkov, H. Peter Anvin, x86, Paolo Bonzini,
	Radim Krčmář, linux-kernel

Replace magic number 0x180 with `EPT_VIOLATION_GVA_IS_VALID | EPT_VIOLATION_GVA_TRANSLATED`
in arch/x86/kvm/mmu/paging_tmpl.h
Similarly, replace `(pte_access & 0x7) << 3` with
`(pte_access & VMX_EPT_RWX_MASK) << EPT_VIOLATION_RWX_SHIFT`.

v1 -> v2: https://lore.kernel.org/kvm/20220321094203.109546-1-darcy.sh@antgroup.com/
- Rename `EPT_VIOLATION_GVA_VALIDATION` to `EPT_VIOLATION_GVA_IS_VALID`. [Sean]
- Using new added `VMX_EPT_RWX_MASK` to replace magic number 0x7 and so on,
  to avoid using branch statement in hotpath. [Sean]

SU Hang (1):
  KVM: VMX:  replace 0x180 with EPT_VIOLATION_* definition

Sean Christopherson (1):
  KVM: x86/mmu: Derive EPT violation RWX bits from EPTE RWX bits

 arch/x86/include/asm/vmx.h     |  9 +++------
 arch/x86/kvm/mmu/paging_tmpl.h | 11 +++++++++--
 arch/x86/kvm/vmx/vmx.c         |  4 +---
 3 files changed, 13 insertions(+), 11 deletions(-)

--
2.32.0.3.g01195cf9f


^ permalink raw reply	[flat|nested] 8+ messages in thread
* Re: [PATCH 2/2] KVM: X86: use EPT_VIOLATION_* instead of 0x7
@ 2022-03-25  0:30 Sean Christopherson
  2022-04-11  4:55 ` [PATCH v2 2/2] KVM: x86/mmu: Derive EPT violation RWX bits from EPTE RWX bits SU Hang
  0 siblings, 1 reply; 8+ messages in thread
From: Sean Christopherson @ 2022-03-25  0:30 UTC (permalink / raw)
  To: SU Hang
  Cc: kvm, 赖江山, Paolo Bonzini, Vitaly Kuznetsov,
	Wanpeng Li, Jim Mattson, Joerg Roedel, Thomas Gleixner,
	Ingo Molnar, Borislav Petkov, Dave Hansen, x86, H. Peter Anvin,
	linux-kernel

On Mon, Mar 21, 2022, SU Hang wrote:
> Use symbolic value, EPT_VIOLATION_*, instead of 0x7
> in FNAME(walk_addr_generic)().
> 
> Signed-off-by: SU Hang <darcy.sh@antgroup.com>
> ---
>  arch/x86/kvm/mmu/paging_tmpl.h | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
> index 7853c7ef13a1..2e2b1f7ccaca 100644
> --- a/arch/x86/kvm/mmu/paging_tmpl.h
> +++ b/arch/x86/kvm/mmu/paging_tmpl.h
> @@ -531,7 +531,12 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
>  			vcpu->arch.exit_qualification |= EPT_VIOLATION_ACC_READ;
>  		if (fetch_fault)
>  			vcpu->arch.exit_qualification |= EPT_VIOLATION_ACC_INSTR;
> -		vcpu->arch.exit_qualification |= (pte_access & 0x7) << 3;

Oof.  I suspect this was done to avoid conditional branches, but more importantly...

> +		if (pte_access & ACC_USER_MASK)
> +			vcpu->arch.exit_qualification |= EPT_VIOLATION_READABLE;
> +		if (pte_access & ACC_WRITE_MASK)
> +			vcpu->arch.exit_qualification |= EPT_VIOLATION_WRITABLE;
> +		if (pte_access & ACC_EXEC_MASK)
> +			vcpu->arch.exit_qualification |= EPT_VIOLATION_EXECUTABLE;

This is subtly wrong.  pte_access is the raw RWX bits out of the EPTE, walker->pte_access
is the version that holds ACC_*_MASK flags after running pte_access through
FNAME(gpte_access).

I'm definitely in favor of a cleanup.  What about formalizing the shift and using
VMX_EPT_RWX_MASK both here and in the generation of the mask for use in KVM's
EPT violation handler?


From: Sean Christopherson <seanjc@google.com>
Date: Thu, 24 Mar 2022 17:23:18 -0700
Subject: [PATCH] KVM: x86/mmu: Derive EPT violation RWX bits from EPTE RWX
 bits

Derive the mask of RWX bits reported on EPT violations from the mask of
RWX bits that are shoved into EPT entries; the layout is the same, the
EPT violation bits are simply shifted by three.  Use the new shift and a
slight copy-paste of the mask derivation instead of completely open
coding the same to convert between the EPT entry bits and the exit
qualification when synthesizing a nested EPT Violation.

No functional change intended.

Cc: SU Hang <darcy.sh@antgroup.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/include/asm/vmx.h     | 8 ++------
 arch/x86/kvm/mmu/paging_tmpl.h | 8 +++++++-
 arch/x86/kvm/vmx/vmx.c         | 4 +---
 3 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index a6789fe9b56e..6c23905d5465 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -543,17 +543,13 @@ enum vm_entry_failure_code {
 #define EPT_VIOLATION_ACC_READ_BIT	0
 #define EPT_VIOLATION_ACC_WRITE_BIT	1
 #define EPT_VIOLATION_ACC_INSTR_BIT	2
-#define EPT_VIOLATION_READABLE_BIT	3
-#define EPT_VIOLATION_WRITABLE_BIT	4
-#define EPT_VIOLATION_EXECUTABLE_BIT	5
+#define EPT_VIOLATION_RWX_SHIFT		3
 #define EPT_VIOLATION_GVA_VALIDATION_BIT 7
 #define EPT_VIOLATION_GVA_TRANSLATED_BIT 8
 #define EPT_VIOLATION_ACC_READ		(1 << EPT_VIOLATION_ACC_READ_BIT)
 #define EPT_VIOLATION_ACC_WRITE		(1 << EPT_VIOLATION_ACC_WRITE_BIT)
 #define EPT_VIOLATION_ACC_INSTR		(1 << EPT_VIOLATION_ACC_INSTR_BIT)
-#define EPT_VIOLATION_READABLE		(1 << EPT_VIOLATION_READABLE_BIT)
-#define EPT_VIOLATION_WRITABLE		(1 << EPT_VIOLATION_WRITABLE_BIT)
-#define EPT_VIOLATION_EXECUTABLE	(1 << EPT_VIOLATION_EXECUTABLE_BIT)
+#define EPT_VIOLATION_RWX_MASK		(VMX_EPT_RWX_MASK << EPT_VIOLATION_RWX_SHIFT)
 #define EPT_VIOLATION_GVA_VALIDATION	(1 << EPT_VIOLATION_GVA_VALIDATION_BIT)
 #define EPT_VIOLATION_GVA_TRANSLATED	(1 << EPT_VIOLATION_GVA_TRANSLATED_BIT)

diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 3c7f2d12b883..90a8e2bb1a3a 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -529,7 +529,13 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
 			vcpu->arch.exit_qualification |= EPT_VIOLATION_ACC_READ;
 		if (fetch_fault)
 			vcpu->arch.exit_qualification |= EPT_VIOLATION_ACC_INSTR;
-		vcpu->arch.exit_qualification |= (pte_access & 0x7) << 3;
+
+		/*
+		 * Note, pte_access holds the raw RWX bits from the EPTE, not
+		 * ACC_*_MASK flags!
+		 */
+		vcpu->arch.exit_qualification |= (pte_access & VMX_EPT_RWX_MASK) <<
+						 EPT_VIOLATION_RWX_SHIFT;
 	}
 #endif
 	walker->fault.address = addr;
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 84a7500cd80c..6c554d2a2038 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5410,9 +5410,7 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu)
 	error_code |= (exit_qualification & EPT_VIOLATION_ACC_INSTR)
 		      ? PFERR_FETCH_MASK : 0;
 	/* ept page table entry is present? */
-	error_code |= (exit_qualification &
-		       (EPT_VIOLATION_READABLE | EPT_VIOLATION_WRITABLE |
-			EPT_VIOLATION_EXECUTABLE))
+	error_code |= (exit_qualification & EPT_VIOLATION_RWX_MASK)
 		      ? PFERR_PRESENT_MASK : 0;

 	error_code |= (exit_qualification & EPT_VIOLATION_GVA_TRANSLATED) != 0 ?

base-commit: 7cd469b5705bcfa65c3055f899c9e3e751053051
--

^ permalink raw reply related	[flat|nested] 8+ messages in thread

end of thread, other threads:[~2022-04-11  4:55 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2022-03-29  3:01 [PATCH v2 0/2] KVM: x86: Replace magic number with readable macro SU Hang
2022-03-29  3:01 ` [PATCH v2 1/2] KVM: VMX: replace 0x180 with EPT_VIOLATION_* definition SU Hang
2022-03-29 16:00   ` Sean Christopherson
2022-03-29  3:01 ` [PATCH v2 2/2] KVM: x86/mmu: Derive EPT violation RWX bits from EPTE RWX bits SU Hang
2022-04-08 21:11   ` Isaku Yamahata
2022-04-08 21:32     ` Sean Christopherson
2022-04-08 16:48 ` [PATCH v2 0/2] KVM: x86: Replace magic number with readable macro Paolo Bonzini
  -- strict thread matches above, loose matches on Subject: below --
2022-03-25  0:30 [PATCH 2/2] KVM: X86: use EPT_VIOLATION_* instead of 0x7 Sean Christopherson
2022-04-11  4:55 ` [PATCH v2 2/2] KVM: x86/mmu: Derive EPT violation RWX bits from EPTE RWX bits SU Hang

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