[PATCH v2] x86/hvm: print valid CR4 bits in case of error

[PATCH v2] x86/hvm: print valid CR4 bits in case of error

[Roger Pau Monne]

Some of the current users of hvm_cr4_guest_valid_bits() don't print
the valid mask in case of error, and thus the resulting error messages
are not as helpful as they could be.

Amend callers to always print the value of hvm_cr4_guest_valid_bits()
together with the rejected bits in the checked value. Also take the
opportunity and adjust all the users to use the same print formatter.

No functional change intended.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
Changes since v1:
 - Use %#lx formatter uniformly.
 - Print rejected bits together with the valid mask.
---
 xen/arch/x86/hvm/domain.c       |  9 ++++++---
 xen/arch/x86/hvm/hvm.c          | 16 +++++++++-------
 xen/arch/x86/hvm/svm/svmdebug.c |  4 ++--
 3 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/xen/arch/x86/hvm/domain.c b/xen/arch/x86/hvm/domain.c
index deec74fdb4f5..efee7fab3e19 100644
--- a/xen/arch/x86/hvm/domain.c
+++ b/xen/arch/x86/hvm/domain.c
@@ -107,6 +107,7 @@ int arch_set_info_hvm_guest(struct vcpu *v, const vcpu_hvm_context_t *ctx)
     struct segment_register cs, ds, ss, es, tr;
     const char *errstr;
     int rc;
+    unsigned long valid;
 
     if ( ctx->pad != 0 )
         return -EINVAL;
@@ -264,10 +265,12 @@ int arch_set_info_hvm_guest(struct vcpu *v, const vcpu_hvm_context_t *ctx)
     if ( v->arch.hvm.guest_efer & EFER_LME )
         v->arch.hvm.guest_efer |= EFER_LMA;
 
-    if ( v->arch.hvm.guest_cr[4] & ~hvm_cr4_guest_valid_bits(d) )
+    valid = hvm_cr4_guest_valid_bits(d);
+    if ( v->arch.hvm.guest_cr[4] & ~valid )
     {
-        gprintk(XENLOG_ERR, "Bad CR4 value: %#016lx\n",
-                v->arch.hvm.guest_cr[4]);
+        gprintk(XENLOG_ERR, "Bad CR4 value: %#lx (valid: %#lx, rejected: %#lx)\n",
+                v->arch.hvm.guest_cr[4], valid,
+                v->arch.hvm.guest_cr[4] & ~valid);
         return -EINVAL;
     }
 
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 2d6e4bb9c682..6fa7046835cf 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -991,6 +991,7 @@ static int cf_check hvm_load_cpu_ctxt(struct domain *d, hvm_domain_context_t *h)
     struct hvm_hw_cpu ctxt;
     struct segment_register seg;
     const char *errstr;
+    unsigned long valid;
 
     /* Which vcpu is this? */
     if ( vcpuid >= d->max_vcpus || (v = d->vcpu[vcpuid]) == NULL )
@@ -1016,10 +1017,11 @@ static int cf_check hvm_load_cpu_ctxt(struct domain *d, hvm_domain_context_t *h)
         return -EINVAL;
     }
 
-    if ( ctxt.cr4 & ~hvm_cr4_guest_valid_bits(d) )
+    valid = hvm_cr4_guest_valid_bits(d);
+    if ( ctxt.cr4 & ~valid )
     {
-        printk(XENLOG_G_ERR "HVM%d restore: bad CR4 %#" PRIx64 "\n",
-               d->domain_id, ctxt.cr4);
+        printk(XENLOG_G_ERR "HVM%d restore: bad CR4 %#lx (valid: %#lx, rejected %#lx)\n",
+               d->domain_id, ctxt.cr4, valid, ctxt.cr4 & ~valid);
         return -EINVAL;
     }
 
@@ -2456,13 +2458,13 @@ int hvm_set_cr3(unsigned long value, bool noflush, bool may_defer)
 int hvm_set_cr4(unsigned long value, bool may_defer)
 {
     struct vcpu *v = current;
-    unsigned long old_cr;
+    unsigned long old_cr, valid = hvm_cr4_guest_valid_bits(v->domain);
 
-    if ( value & ~hvm_cr4_guest_valid_bits(v->domain) )
+    if ( value & ~valid )
     {
         HVM_DBG_LOG(DBG_LEVEL_1,
-                    "Guest attempts to set reserved bit in CR4: %lx",
-                    value);
+                    "Guest attempts to set reserved bit in CR4: %#lx (valid: %#lx, rejected %#lx)",
+                    value, valid, value & ~valid);
         return X86EMUL_EXCEPTION;
     }
 
diff --git a/xen/arch/x86/hvm/svm/svmdebug.c b/xen/arch/x86/hvm/svm/svmdebug.c
index 7d6dc9ef47db..de046ed929a8 100644
--- a/xen/arch/x86/hvm/svm/svmdebug.c
+++ b/xen/arch/x86/hvm/svm/svmdebug.c
@@ -124,8 +124,8 @@ bool svm_vmcb_isvalid(const char *from, const struct vmcb_struct *vmcb,
 
     valid = hvm_cr4_guest_valid_bits(v->domain);
     if ( cr4 & ~valid )
-        PRINTF("CR4: invalid bits are set (%#"PRIx64", valid: %#"PRIx64")\n",
-               cr4, valid);
+        PRINTF("CR4: invalid value: %#lx (valid: %#lx, rejected: %#lx)\n",
+               cr4, valid, cr4 & ~valid);
 
     if ( vmcb_get_dr6(vmcb) >> 32 )
         PRINTF("DR6: bits [63:32] are not zero (%#"PRIx64")\n",
-- 
2.40.0

Re: [PATCH v2] x86/hvm: print valid CR4 bits in case of error

[Andrew Cooper]

On 08/06/2023 10:59 am, Roger Pau Monne wrote:
> Some of the current users of hvm_cr4_guest_valid_bits() don't print
> the valid mask in case of error, and thus the resulting error messages
> are not as helpful as they could be.
>
> Amend callers to always print the value of hvm_cr4_guest_valid_bits()
> together with the rejected bits in the checked value. Also take the
> opportunity and adjust all the users to use the same print formatter.
>
> No functional change intended.
>
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>

Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>