From: Kai Huang <kai.huang@intel.com>
To: Dave Hansen <dave.hansen@intel.com>,
Sathyanarayanan Kuppuswamy
<sathyanarayanan.kuppuswamy@linux.intel.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Tony Luck <tony.luck@intel.com>, Andi Kleen <ak@linux.intel.com>,
Wander Lairson Costa <wander@redhat.com>,
Isaku Yamahata <isaku.yamahata@gmail.com>,
marcelo.cerri@canonical.com, tim.gardner@canonical.com,
khalid.elmously@canonical.com, philip.cox@canonical.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 3/3] x86/tdx: Add Quote generation support
Date: Fri, 06 May 2022 23:00:29 +1200 [thread overview]
Message-ID: <c3003e378504d2cd034e54bca6cab4d6bb53e008.camel@intel.com> (raw)
In-Reply-To: <d63d2774-c44d-27da-74b6-550935a196fd@intel.com>
On Thu, 2022-05-05 at 16:06 -0700, Dave Hansen wrote:
> On 5/5/22 15:15, Kai Huang wrote:
> > set_memory_xx() is supposedly only for direct-mapping. Please use my
> > suggestion above.
>
> Kai, please take a look at some of the other users, especially
> set_memory_x(). See how long the "supposed" requirement holds up.
>
> That said, I've forgotten by now if this _could_ have used vmalloc() or
> vmap() or vmap_pfn(). None of the logic about why or how the allocator
> and mapping design decisions were made. Could that be be rectified for
> the next post?
Hi Dave,
(Sorry previous reply was too fast..)
I spent some time looking into how __change_page_attr_set_clr() is implemented,
which is called by all set_memory_xxx() variants. If my understanding is
correct, __change_page_attr_set_clr() will work for vmap() variants, because it
internally uses lookup_address(), which walks the page table directly, to find
the actual PTE (and PFN). So set_memory_decrypted() can be fixed to support
vmap() mapping for TDX.
However, looking at the code, set_memory_decrypted() calls
__change_page_attr_set_clr(&cpa, 1). The second argument is 'checkalias', which
means even we call set_memory_decrypted() against vmap() address, the aliasing
mappings will be changed too. And if I understand correctly, the aliasing
mapping includes direct-mapping too:
static int cpa_process_alias(struct cpa_data *cpa)
{
struct cpa_data alias_cpa;
unsigned long laddr = (unsigned long)__va(cpa->pfn << PAGE_SHIFT);
unsigned long vaddr;
int ret;
if (!pfn_range_is_mapped(cpa->pfn, cpa->pfn + 1))
return 0;
/*
* No need to redo, when the primary call touched the direct
* mapping already:
*/
vaddr = __cpa_addr(cpa, cpa->curpage);
if (!(within(vaddr, PAGE_OFFSET,
PAGE_OFFSET + (max_pfn_mapped << PAGE_SHIFT)))) {
alias_cpa = *cpa;
alias_cpa.vaddr = &laddr;
alias_cpa.flags &= ~(CPA_PAGES_ARRAY | CPA_ARRAY);
alias_cpa.curpage = 0;
cpa->force_flush_all = 1;
ret = __change_page_attr_set_clr(&alias_cpa, 0);
if (ret)
return ret;
}
#ifdef CONFIG_X86_64
/*
* If the primary call didn't touch the high mapping already
* and the physical address is inside the kernel map, we need
* to touch the high mapped kernel as well:
*/
if (!within(vaddr, (unsigned long)_text, _brk_end) &&
__cpa_pfn_in_highmap(cpa->pfn)) {
unsigned long temp_cpa_vaddr = (cpa->pfn << PAGE_SHIFT) +
__START_KERNEL_map - phys_base;
alias_cpa = *cpa;
alias_cpa.vaddr = &temp_cpa_vaddr;
alias_cpa.flags &= ~(CPA_PAGES_ARRAY | CPA_ARRAY);
alias_cpa.curpage = 0;
cpa->force_flush_all = 1;
/*
* The high mapping range is imprecise, so ignore the
* return value.
*/
__change_page_attr_set_clr(&alias_cpa, 0);
}
#endif
return 0;
}
As you can see, the first chunk checks whether the virtual address is direct-
mapping, and if it is not, direct mapping is changed too.
The second chunk even changes the high kernel mapping.
So, if we use set_memory_decrypted(), there's no difference whether the address
is vmap() or direct mapping address. The direct mapping will be changed anyway.
(However, it seems if we call set_memory_decrypted() against direct mapping
address, the vmap() mapping won't be impacted, because it seems
cpa_process_alias() doesn't check vmap() area..).
However I may have missed something. Kirill please help to confirm if you see
this.
--
Thanks,
-Kai
next prev parent reply other threads:[~2022-05-06 11:00 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-01 18:34 [PATCH v5 0/3] Add TDX Guest Attestation support Kuppuswamy Sathyanarayanan
2022-05-01 18:34 ` [PATCH v5 1/3] x86/tdx: Add TDX Guest attestation interface driver Kuppuswamy Sathyanarayanan
2022-05-02 2:31 ` Kai Huang
2022-05-02 15:52 ` Sathyanarayanan Kuppuswamy
2022-05-02 22:30 ` Kai Huang
2022-05-02 23:17 ` Sathyanarayanan Kuppuswamy
2022-05-02 23:37 ` Kai Huang
2022-05-03 14:38 ` Wander Costa
2022-05-03 15:09 ` Sathyanarayanan Kuppuswamy
2022-05-03 22:08 ` Kai Huang
2022-05-02 12:18 ` Wander Lairson Costa
2022-05-02 16:06 ` Sathyanarayanan Kuppuswamy
2022-05-01 18:34 ` [PATCH v5 2/3] x86/tdx: Add TDX Guest event notify interrupt support Kuppuswamy Sathyanarayanan
2022-05-02 12:44 ` Wander Lairson Costa
2022-05-01 18:35 ` [PATCH v5 3/3] x86/tdx: Add Quote generation support Kuppuswamy Sathyanarayanan
2022-05-02 2:40 ` Kai Huang
2022-05-03 1:27 ` Kirill A. Shutemov
2022-05-03 2:18 ` Kai Huang
2022-05-03 2:39 ` Sathyanarayanan Kuppuswamy
2022-05-03 22:13 ` Kai Huang
2022-05-03 2:45 ` Kirill A. Shutemov
2022-05-03 3:36 ` Kai Huang
2022-05-03 22:24 ` Dave Hansen
2022-05-03 22:28 ` Sathyanarayanan Kuppuswamy
2022-05-03 22:30 ` Sathyanarayanan Kuppuswamy
2022-05-04 22:49 ` Sathyanarayanan Kuppuswamy
2022-05-04 23:28 ` Kai Huang
2022-05-05 20:53 ` Sathyanarayanan Kuppuswamy
2022-05-05 22:15 ` Kai Huang
2022-05-05 22:38 ` Sathyanarayanan Kuppuswamy
2022-05-05 23:06 ` Dave Hansen
2022-05-06 0:11 ` Kai Huang
2022-05-06 1:55 ` Sathyanarayanan Kuppuswamy
2022-05-07 0:42 ` Kirill A. Shutemov
2022-05-09 3:37 ` Kai Huang
2022-05-09 12:09 ` Kirill A. Shutemov
2022-05-09 14:14 ` Dave Hansen
2022-05-09 15:35 ` Kirill A. Shutemov
2022-05-09 15:43 ` Sathyanarayanan Kuppuswamy
2022-05-09 23:54 ` Kai Huang
2022-05-10 0:17 ` Sathyanarayanan Kuppuswamy
2022-05-10 1:30 ` Kirill A. Shutemov
2022-05-10 1:40 ` Kai Huang
2022-05-10 10:42 ` Kai Huang
2022-05-16 17:39 ` Sathyanarayanan Kuppuswamy
2022-05-06 11:00 ` Kai Huang [this message]
2022-05-06 15:47 ` Dave Hansen
2022-05-07 1:00 ` Kirill A. Shutemov
2022-05-05 10:50 ` Kai Huang
2022-05-05 19:03 ` Sathyanarayanan Kuppuswamy
2022-05-05 22:25 ` Kai Huang
2022-05-02 5:01 ` Kai Huang
2022-05-02 16:02 ` Sathyanarayanan Kuppuswamy
2022-05-02 23:02 ` Kai Huang
2022-05-02 13:16 ` Wander Lairson Costa
2022-05-02 16:05 ` Sathyanarayanan Kuppuswamy
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