From 26d074fdbf3da16e38bd7898d29ac8480e71e5d7 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Tue, 24 Jun 2014 10:17:45 +0200 Subject: [PATCH] x86/HVM: refine SMEP test in HVM_CR4_GUEST_RESERVED_BITS() Andrew validly points out that the use of the macro on the restore path can't rely on the CPUID bits for the guest already being in place (as their setting by the tool stack in turn requires the other restore operations already having taken place). And even worse, using hvm_cpuid() is invalid here because that function assumes to be used in the context of the vCPU in question. Reverting to the behavior prior to the change from checking cpu_has_sm?p to hvm_vcpu_has_sm?p() would break the other (non-restore) use of the macro. So let's revert to the prior behavior only for the restore path, by adding a respective second parameter to the macro. Obviously the two cpu_has_* uses in the macro should really also be converted to hvm_cpuid() based checks at least for the non-restore path. Reported-by: Andrew Cooper Signed-off-by: Jan Beulich Tested-by: David Vrabel master commit: 584287380baf81e5acdd9dc7dfc7ffccd1e9a856 master date: 2014-06-10 13:12:05 +0200 --- xen/arch/x86/hvm/hvm.c | 4 ++-- xen/include/asm-x86/hvm/hvm.h | 18 ++++++++++++------ 2 files changed, 14 insertions(+), 8 deletions(-) diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c index 68531abdc0..7d4b0b390c 100644 --- a/xen/arch/x86/hvm/hvm.c +++ b/xen/arch/x86/hvm/hvm.c @@ -751,7 +751,7 @@ static int hvm_load_cpu_ctxt(struct domain *d, hvm_domain_context_t *h) return -EINVAL; } - if ( ctxt.cr4 & HVM_CR4_GUEST_RESERVED_BITS(v) ) + if ( ctxt.cr4 & HVM_CR4_GUEST_RESERVED_BITS(v, 1) ) { printk(XENLOG_G_ERR "HVM%d restore: bad CR4 %#" PRIx64 "\n", d->domain_id, ctxt.cr4); @@ -1842,7 +1842,7 @@ int hvm_set_cr4(unsigned long value) struct vcpu *v = current; unsigned long old_cr; - if ( value & HVM_CR4_GUEST_RESERVED_BITS(v) ) + if ( value & HVM_CR4_GUEST_RESERVED_BITS(v, 0) ) { HVM_DBG_LOG(DBG_LEVEL_1, "Guest attempts to set reserved bit in CR4: %lx", diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h index 902f224859..d6bb84420d 100644 --- a/xen/include/asm-x86/hvm/hvm.h +++ b/xen/include/asm-x86/hvm/hvm.h @@ -365,18 +365,24 @@ static inline bool_t hvm_vcpu_has_smep(void) (X86_CR4_VMXE | X86_CR4_PAE | X86_CR4_MCE)) /* These bits in CR4 cannot be set by the guest. */ -#define HVM_CR4_GUEST_RESERVED_BITS(_v) \ +#define HVM_CR4_GUEST_RESERVED_BITS(v, restore) ({ \ + const struct vcpu *_v = (v); \ + bool_t _restore = !!(restore); \ + ASSERT((_restore) || _v == current); \ (~((unsigned long) \ (X86_CR4_VME | X86_CR4_PVI | X86_CR4_TSD | \ X86_CR4_DE | X86_CR4_PSE | X86_CR4_PAE | \ X86_CR4_MCE | X86_CR4_PGE | X86_CR4_PCE | \ X86_CR4_OSFXSR | X86_CR4_OSXMMEXCPT | \ - (hvm_vcpu_has_smep() ? X86_CR4_SMEP : 0) | \ + (((_restore) ? cpu_has_smep : \ + hvm_vcpu_has_smep()) ? \ + X86_CR4_SMEP : 0) | \ (cpu_has_fsgsbase ? X86_CR4_FSGSBASE : 0) | \ - ((nestedhvm_enabled((_v)->domain) && cpu_has_vmx)\ - ? X86_CR4_VMXE : 0) | \ - (cpu_has_pcid ? X86_CR4_PCIDE : 0) | \ - (cpu_has_xsave ? X86_CR4_OSXSAVE : 0)))) + ((nestedhvm_enabled(_v->domain) && cpu_has_vmx) \ + ? X86_CR4_VMXE : 0) | \ + (cpu_has_pcid ? X86_CR4_PCIDE : 0) | \ + (cpu_has_xsave ? X86_CR4_OSXSAVE : 0)))); \ +}) /* These exceptions must always be intercepted. */ #define HVM_TRAP_MASK ((1U << TRAP_machine_check) | (1U << TRAP_invalid_op)) -- 2.39.5