Messages in this thread | | | From | "Michael Kelley (LINUX)" <> | Subject | RE: [PATCH v2 2/8] x86/mtrr: support setting MTRR state for software defined MTRRs | Date | Mon, 13 Feb 2023 01:07:47 +0000 |
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From: Juergen Gross <jgross@suse.com> Sent: Wednesday, February 8, 2023 11:22 PM > > When running virtualized, MTRR access can be reduced (e.g. in Xen PV > guests or when running as a SEV-SNP guest under Hyper-V). Typically > the hypervisor will reset the MTRR feature in cpuid data, resulting > in no MTRR memory type information being available for the kernel. > > This has turned out to result in problems: > > - Hyper-V SEV-SNP guests using uncached mappings where they shouldn't > - Xen PV dom0 mapping memory as WB which should be UC- instead > > Solve those problems by supporting to set a fixed MTRR state, > overwriting the empty state used today. In case such a state has been > set, don't call get_mtrr_state() in mtrr_bp_init(). The set state > will only be used by mtrr_type_lookup(), as in all other cases > mtrr_enabled() is being checked, which will return false. Accept the > overwrite call only in case of MTRRs being disabled in cpuid. > > Signed-off-by: Juergen Gross <jgross@suse.com> > --- > V2: > - new patch > --- > arch/x86/include/asm/mtrr.h | 2 ++ > arch/x86/kernel/cpu/mtrr/generic.c | 38 ++++++++++++++++++++++++++++++ > arch/x86/kernel/cpu/mtrr/mtrr.c | 9 +++++++ > 3 files changed, 49 insertions(+) > > diff --git a/arch/x86/include/asm/mtrr.h b/arch/x86/include/asm/mtrr.h > index f0eeaf6e5f5f..0b8f51d683dc 100644 > --- a/arch/x86/include/asm/mtrr.h > +++ b/arch/x86/include/asm/mtrr.h > @@ -31,6 +31,8 @@ > */ > # ifdef CONFIG_MTRR > void mtrr_bp_init(void); > +void mtrr_overwrite_state(struct mtrr_var_range *var, unsigned int num_var, > + mtrr_type *fixed, mtrr_type def_type);
Could you add a stub for the !CONFIG_MTRR case? Then the #ifdef CONFIG_MTRR could be removed in Patch 3 of this series.
Michael
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