From: Juergen Gross <jgross@xxxxxxxx> Sent: Wednesday, February 8, 2023 11:22 PM
In order to avoid mappings using the UC- cache attribute, set the
MTRR state to use WB caching as the default.
This is needed in order to cope with the fact that PAT is enabled,
while MTRRs are disabled by the hypervisor.
Fixes: 90b926e68f50 ("x86/pat: Fix pat_x_mtrr_type() for MTRR disabled case")
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V2:
- new patch
---
arch/x86/kernel/cpu/mshyperv.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 46668e255421..51e47dc0e987 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -34,6 +34,7 @@
#include <clocksource/hyperv_timer.h>
#include <asm/numa.h>
#include <asm/coco.h>
+#include <asm/mtrr.h>
/* Is Linux running as the root partition? */
bool hv_root_partition;
@@ -335,6 +336,13 @@ static void __init ms_hyperv_init_platform(void)
static_branch_enable(&isolation_type_snp);
#ifdef CONFIG_SWIOTLB
swiotlb_unencrypted_base = ms_hyperv.shared_gpa_boundary;
+#endif
Unfortunately, Hyper-V does not filter out the MTRR flag from the
CPUID leaf, so this code also needs
setup_clear_cpu_cap(X86_FEATURE_MTRR);
before calling mtrr_overwrite_state(). I've got a bug filed for the
Hyper-V team to fix the flag, but clearing the feature here solves the
problem regardless.
+#ifdef CONFIG_MTRR
Hopefully this #ifdef can go away, per my comment in Patch 2 of
the series.
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