[xen master] x86/boot: Sanitise PKRU on boot

[patchbot@xxxxxxx]

commit c4f9a3bad3f1c6e34c61ad8103a4145f2d6f9c68
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Tue Jan 10 10:57:21 2023 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Fri Jan 20 19:39:32 2023 +0000

    x86/boot: Sanitise PKRU on boot
    
    While the reset value of the register is 0, it might not be after kexec/etc.
    If PKEY0.{WD,AD} have leaked in from an earlier context, construction of a 
PV
    dom0 will explode.
    
    Sequencing wise, this must come after setting CR4.PKE, and before we touch 
any
    user mappings.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/cpu/common.c             | 3 +++
 xen/arch/x86/include/asm/cpufeature.h | 1 +
 xen/arch/x86/setup.c                  | 2 +-
 3 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index 0412dbc915..fe92f29c2d 100644
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -936,6 +936,9 @@ void cpu_init(void)
        write_debugreg(6, X86_DR6_DEFAULT);
        write_debugreg(7, X86_DR7_DEFAULT);
 
+       if (cpu_has_pku)
+               wrpkru(0);
+
        /*
         * If the platform is performing a Secure Launch via SKINIT, GIF is
         * clear to prevent external interrupts interfering with Secure
diff --git a/xen/arch/x86/include/asm/cpufeature.h 
b/xen/arch/x86/include/asm/cpufeature.h
index a3ad9ebee4..044cfd9f88 100644
--- a/xen/arch/x86/include/asm/cpufeature.h
+++ b/xen/arch/x86/include/asm/cpufeature.h
@@ -109,6 +109,7 @@
 
 /* CPUID level 0x00000007:0.ecx */
 #define cpu_has_avx512_vbmi     boot_cpu_has(X86_FEATURE_AVX512_VBMI)
+#define cpu_has_pku             boot_cpu_has(X86_FEATURE_PKU)
 #define cpu_has_avx512_vbmi2    boot_cpu_has(X86_FEATURE_AVX512_VBMI2)
 #define cpu_has_gfni            boot_cpu_has(X86_FEATURE_GFNI)
 #define cpu_has_vaes            boot_cpu_has(X86_FEATURE_VAES)
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 566422600d..6deadcf747 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -1798,7 +1798,7 @@ void __init noreturn __start_xen(unsigned long mbi_p)
     if ( boot_cpu_has(X86_FEATURE_FSGSBASE) )
         set_in_cr4(X86_CR4_FSGSBASE);
 
-    if ( boot_cpu_has(X86_FEATURE_PKU) )
+    if ( cpu_has_pku )
         set_in_cr4(X86_CR4_PKE);
 
     if ( opt_invpcid && cpu_has_invpcid )
--
generated by git-patchbot for /home/xen/git/xen.git#master