Messages in this thread | | | Date | Thu, 16 Feb 2023 03:07:28 -0800 | From | Jeremi Piotrowski <> | Subject | Re: [PATCH v2 2/8] x86/mtrr: support setting MTRR state for software defined MTRRs |
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On Mon, Feb 13, 2023 at 12:39:40PM +0100, Borislav Petkov wrote: > On Thu, Feb 09, 2023 at 08:22:14AM +0100, Juergen Gross wrote: > > 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. > > s/cpuid/CPUID/g > > > 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); > > extern u8 mtrr_type_lookup(u64 addr, u64 end, u8 *uniform); > > extern void mtrr_save_fixed_ranges(void *); > > extern void mtrr_save_state(void); > > diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c > > index ee09d359e08f..788bc16888a5 100644 > > --- a/arch/x86/kernel/cpu/mtrr/generic.c > > +++ b/arch/x86/kernel/cpu/mtrr/generic.c > > @@ -240,6 +240,44 @@ static u8 mtrr_type_lookup_variable(u64 start, u64 end, u64 *partial_end, > > return mtrr_state.def_type; > > } > > > > +/** > > + * mtrr_overwrite_state - set fixed MTRR state > > fixed only? You pass in variable too... > > > + * > > + * Used to set MTRR state via different means (e.g. with data obtained from > > + * a hypervisor). > > + */ > > +void mtrr_overwrite_state(struct mtrr_var_range *var, unsigned int num_var, > > + mtrr_type *fixed, mtrr_type def_type) > > +{ > > + unsigned int i; > > + > > + if (boot_cpu_has(X86_FEATURE_MTRR)) > > check_for_deprecated_apis: WARNING: arch/x86/kernel/cpu/mtrr/generic.c:254: Do not use boot_cpu_has() - use cpu_feature_enabled() instead. >
Hi Boris,
Where does this check come from? I can't find a source for it.
Jeremi
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