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Message-ID: <c6fe82c6-060e-f16f-bbeb-25d85948c4c7@amd.com>
Date: Mon, 20 Apr 2020 13:30:18 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: Jürgen Groß <jgross@...e.com>,
Thomas Gleixner <tglx@...utronix.de>,
LKML <linux-kernel@...r.kernel.org>
Cc: x86@...nel.org, Kees Cook <keescook@...omium.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: Re: [patch 05/15] x86/tlb: Move __flush_tlb() out of line
On 4/20/20 9:38 AM, Jürgen Groß wrote:
> On 20.04.20 16:26, Tom Lendacky wrote:
>> On 4/20/20 9:03 AM, Jürgen Groß wrote:
>>> On 20.04.20 15:48, Tom Lendacky wrote:
>>>> On 4/19/20 3:31 PM, Thomas Gleixner wrote:
>>>>> cpu_tlbstate is exported because various TLB related functions need
>>>>> access
>>>>> to it, but cpu_tlbstate is sensitive information which should only be
>>>>> accessed by well contained kernel functions and not be directly
>>>>> exposed to
>>>>> modules.
>>>>>
>>>>> The various TLB flush functions need access to cpu_tlbstate. As a first
>>>>> step move __flush_tlb() out of line and hide the native function. The
>>>>> latter can be static when CONFIG_PARAVIRT is disabled.
>>>>>
>>>>> Consolidate the name space while at it and remove the pointless extra
>>>>> wrapper in the paravirt code.
>>>>>
>>>>> No functional change.
>>>>>
>>>>> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
>>>>> Cc: Thomas Lendacky <Thomas.Lendacky@....com>
>>>>> Cc: Juergen Gross <jgross@...e.com>
>>>>> ---
>>>>> arch/x86/include/asm/paravirt.h | 4 +++-
>>>>> arch/x86/include/asm/tlbflush.h | 29
>>>>> +++++------------------------
>>>>> arch/x86/kernel/cpu/mtrr/generic.c | 4 ++--
>>>>> arch/x86/kernel/paravirt.c | 7 +------
>>>>> arch/x86/mm/mem_encrypt.c | 2 +-
>>>>> arch/x86/mm/tlb.c | 33
>>>>> ++++++++++++++++++++++++++++++++-
>>>>> arch/x86/platform/uv/tlb_uv.c | 2 +-
>>>>> 7 files changed, 45 insertions(+), 36 deletions(-)
>>>>>
>>>>> --- a/arch/x86/include/asm/paravirt.h
>>>>> +++ b/arch/x86/include/asm/paravirt.h
>>>>> @@ -47,7 +47,9 @@ static inline void slow_down_io(void)
>>>>> #endif
>>>>> }
>>>>> -static inline void __flush_tlb(void)
>>>>> +void native_flush_tlb_local(void);
>>>>> +
>>>>> +static inline void __flush_tlb_local(void)
>>>>> {
>>>>> PVOP_VCALL0(mmu.flush_tlb_user);
>>>>> }
>>>>> --- a/arch/x86/include/asm/tlbflush.h
>>>>> +++ b/arch/x86/include/asm/tlbflush.h
>>>>> @@ -140,12 +140,13 @@ static inline unsigned long build_cr3_no
>>>>> return __sme_pa(pgd) | kern_pcid(asid) | CR3_NOFLUSH;
>>>>> }
>>>>> +void flush_tlb_local(void);
>>>>> +
>>>>> #ifdef CONFIG_PARAVIRT
>>>>> #include <asm/paravirt.h>
>>>>> #else
>>>>> -#define __flush_tlb() __native_flush_tlb()
>>>>> -#define __flush_tlb_global() __native_flush_tlb_global()
>>>>> -#define __flush_tlb_one_user(addr) __native_flush_tlb_one_user(addr)
>>>>> +#define __flush_tlb_global() __native_flush_tlb_global()
>>>>> +#define __flush_tlb_one_user(addr) __native_flush_tlb_one_user(addr)
>>>>> #endif
>>>>> struct tlb_context {
>>>>> @@ -371,24 +372,6 @@ static inline void invalidate_user_asid(
>>>>> }
>>>>> /*
>>>>> - * flush the entire current user mapping
>>>>> - */
>>>>> -static inline void __native_flush_tlb(void)
>>>>> -{
>>>>> - /*
>>>>> - * Preemption or interrupts must be disabled to protect the access
>>>>> - * to the per CPU variable and to prevent being preempted between
>>>>> - * read_cr3() and write_cr3().
>>>>> - */
>>>>> - WARN_ON_ONCE(preemptible());
>>>>> -
>>>>> - invalidate_user_asid(this_cpu_read(cpu_tlbstate.loaded_mm_asid));
>>>>> -
>>>>> - /* If current->mm == NULL then the read_cr3() "borrows" an mm */
>>>>> - native_write_cr3(__native_read_cr3());
>>>>> -}
>>>>> -
>>>>> -/*
>>>>> * flush everything
>>>>> */
>>>>> static inline void __native_flush_tlb_global(void)
>>>>> @@ -461,7 +444,7 @@ static inline void __flush_tlb_all(void)
>>>>> /*
>>>>> * !PGE -> !PCID (setup_pcid()), thus every flush is total.
>>>>> */
>>>>> - __flush_tlb();
>>>>> + flush_tlb_local();
>>>>> }
>>>>> }
>>>>> @@ -537,8 +520,6 @@ struct flush_tlb_info {
>>>>> bool freed_tables;
>>>>> };
>>>>> -#define local_flush_tlb() __flush_tlb()
>>>>> -
>>>>> #define flush_tlb_mm(mm) \
>>>>> flush_tlb_mm_range(mm, 0UL, TLB_FLUSH_ALL, 0UL, true)
>>>>> --- a/arch/x86/kernel/cpu/mtrr/generic.c
>>>>> +++ b/arch/x86/kernel/cpu/mtrr/generic.c
>>>>> @@ -761,7 +761,7 @@ static void prepare_set(void) __acquires
>>>>> /* Flush all TLBs via a mov %cr3, %reg; mov %reg, %cr3 */
>>>>> count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
>>>>> - __flush_tlb();
>>>>> + flush_tlb_local();
>>>>> /* Save MTRR state */
>>>>> rdmsr(MSR_MTRRdefType, deftype_lo, deftype_hi);
>>>>> @@ -778,7 +778,7 @@ static void post_set(void) __releases(se
>>>>> {
>>>>> /* Flush TLBs (no need to flush caches - they are disabled) */
>>>>> count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
>>>>> - __flush_tlb();
>>>>> + flush_tlb_local();
>>>>> /* Intel (P6) standard MTRRs */
>>>>> mtrr_wrmsr(MSR_MTRRdefType, deftype_lo, deftype_hi);
>>>>> --- a/arch/x86/kernel/paravirt.c
>>>>> +++ b/arch/x86/kernel/paravirt.c
>>>>> @@ -160,11 +160,6 @@ unsigned paravirt_patch_insns(void *insn
>>>>> return insn_len;
>>>>> }
>>>>> -static void native_flush_tlb(void)
>>>>> -{
>>>>> - __native_flush_tlb();
>>>>> -}
>>>>> -
>>>>> /*
>>>>> * Global pages have to be flushed a bit differently. Not a real
>>>>> * performance problem because this does not happen often.
>>>>> @@ -359,7 +354,7 @@ struct paravirt_patch_template pv_ops =
>>>>> #endif /* CONFIG_PARAVIRT_XXL */
>>>>> /* Mmu ops. */
>>>>> - .mmu.flush_tlb_user = native_flush_tlb,
>>>>> + .mmu.flush_tlb_user = native_flush_tlb_local,
>>>>> .mmu.flush_tlb_kernel = native_flush_tlb_global,
>>>>> .mmu.flush_tlb_one_user = native_flush_tlb_one_user,
>>>>> .mmu.flush_tlb_others = native_flush_tlb_others,
>>>>> --- a/arch/x86/mm/mem_encrypt.c
>>>>> +++ b/arch/x86/mm/mem_encrypt.c
>>>>> @@ -134,7 +134,7 @@ static void __init __sme_early_map_unmap
>>>>> size = (size <= PMD_SIZE) ? 0 : size - PMD_SIZE;
>>>>> } while (size);
>>>>> - __native_flush_tlb();
>>>>> + flush_tlb_local();
>>>>
>>>> This invoked __native_flush_tlb() because of how early it is called
>>>> and the paravirt ops support isn't set up yet, resulting in a crash if
>>>> not invoking the native version directly. So this needs a "native"
>>>> version of the tlb flush to invoke.
>>>
>>> I don't think this is still true. With my rework of pvops to have all
>>> functions in one struct which is initialized statically initially
>>> everything should work from the time the kernel is mapped.
>>>
>>> In case it doesn't there is something very wrong IMO.
>>
>> The memory encryption support was implemented in 4.14, so it's quite
>> possible that this isn't an issue now. I'll test out the patch and
>> verify it. What release did your pvops rework land in?
>
> 4.20.
Ok, my (limited) testing appears good at this point. I see a couple of
calls to ftrace (__fentry__) that just return before invoking the native
version of the TLB flushing function.
I don't remember what the original problem was that required the call to
__native_flush_tlb(), maybe some overall kernel instrumentation that once
removed via the Makefile took care of it. But it appears ok now, so
disregard my original comment.
Thanks,
Tom
>
>
> Juergen
>
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