Re: [PATCH 2/2] Remove the memory encryption mask to obtain the true physical address

["dyoung@redhat.com" <dyoung@redhat.com>]

+ Tom
On 01/25/19 at 11:06am, lijiang wrote:
> 在 2019年01月24日 06:16, Kazuhito Hagio 写道:
> > On 1/22/2019 3:03 AM, Lianbo Jiang wrote:
> >> For AMD machine with SME feature, if SME is enabled in the first
> >> kernel, the crashed kernel's page table(pgd/pud/pmd/pte) contains
> >> the memory encryption mask, so makedumpfile needs to remove the
> >> memory encryption mask to obtain the true physical address.
> >>
> >> Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
> >> ---
> >>  arch/x86_64.c  | 3 +++
> >>  makedumpfile.c | 1 +
> >>  2 files changed, 4 insertions(+)
> >>
> >> diff --git a/arch/x86_64.c b/arch/x86_64.c
> >> index 537fb78..7651d36 100644
> >> --- a/arch/x86_64.c
> >> +++ b/arch/x86_64.c
> >> @@ -346,6 +346,7 @@ __vtop4_x86_64(unsigned long vaddr, unsigned long pagetable)
> >>  			return NOT_PADDR;
> >>  		}
> >>  		pud_paddr  = pgd & ENTRY_MASK;
> >> +		pud_paddr = pud_paddr & ~(NUMBER(sme_mask));
> >>  	}
> >>
> >>  	/*
> >> @@ -371,6 +372,7 @@ __vtop4_x86_64(unsigned long vaddr, unsigned long pagetable)
> >>  	 * Get PMD.
> >>  	 */
> >>  	pmd_paddr  = pud_pte & ENTRY_MASK;
> >> +	pmd_paddr = pmd_paddr & ~(NUMBER(sme_mask));
> >>  	pmd_paddr += pmd_index(vaddr) * sizeof(unsigned long);
> >>  	if (!readmem(PADDR, pmd_paddr, &pmd_pte, sizeof pmd_pte)) {
> >>  		ERRMSG("Can't get pmd_pte (pmd_paddr:%lx).\n", pmd_paddr);
> >> @@ -391,6 +393,7 @@ __vtop4_x86_64(unsigned long vaddr, unsigned long pagetable)
> >>  	 * Get PTE.
> >>  	 */
> >>  	pte_paddr  = pmd_pte & ENTRY_MASK;
> >> +	pte_paddr = pte_paddr & ~(NUMBER(sme_mask));
> >>  	pte_paddr += pte_index(vaddr) * sizeof(unsigned long);
> >>  	if (!readmem(PADDR, pte_paddr, &pte, sizeof pte)) {
> >>  		ERRMSG("Can't get pte (pte_paddr:%lx).\n", pte_paddr);
> >> diff --git a/makedumpfile.c b/makedumpfile.c
> >> index a03aaa1..81c7bb4 100644
> >> --- a/makedumpfile.c
> >> +++ b/makedumpfile.c
> >> @@ -977,6 +977,7 @@ next_page:
> >>  	read_size = MIN(info->page_size - PAGEOFFSET(paddr), size);
> >>
> >>  	pgaddr = PAGEBASE(paddr);
> >> +	pgaddr = pgaddr & ~(NUMBER(sme_mask));
> > 
> > Since NUMBER(sme_mask) is initialized with -1 (NOT_FOUND_NUMBER),
> > if the sme_mask is not in vmcoreinfo, ~(NUMBER(sme_mask)) will be 0.
> > So the four lines added above need
> > 
> >   if (NUMBER(sme_mask) != NOT_FOUND_NUMBER)
> >     ...
> > 
> 
> Thank you very much for pointing out my mistake.
> 
> I will improve it and post again.
> 
> > and, what I'm wondering is whether it doesn't need to take hugepages
> > into account such as this
> > 
> > 392         if (pmd_pte & _PAGE_PSE)        /* 2MB pages */
> > 393                 return (pmd_pte & ENTRY_MASK & PMD_MASK) +
> > 394                         (vaddr & ~PMD_MASK);
> > "arch/x86_64.c"
> > 
> 
> This is a good question. Theoretically, it should be modified accordingly for
> huge pages case.
> 
> But makedumpfile still works well without this change. And i'm sure that the
> huge pages are enabled in crashed kernel. This is very strange.
> 
> Thanks.
> Lianbo
> 
> > Thanks,
> > Kazu
> > 
> > 
> >>  	pgbuf = cache_search(pgaddr, read_size);
> >>  	if (!pgbuf) {
> >>  		++cache_miss;
> >> --
> >> 2.17.1
> >>
> > 
> > 

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