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Date: Tue, 22 Feb 2022 14:03:12 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Dave Hansen <dave.hansen@...el.com>
Cc: tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
luto@...nel.org, peterz@...radead.org,
sathyanarayanan.kuppuswamy@...ux.intel.com, aarcange@...hat.com,
ak@...ux.intel.com, dan.j.williams@...el.com, david@...hat.com,
hpa@...or.com, jgross@...e.com, jmattson@...gle.com,
joro@...tes.org, jpoimboe@...hat.com, knsathya@...nel.org,
pbonzini@...hat.com, sdeep@...are.com, seanjc@...gle.com,
tony.luck@...el.com, vkuznets@...hat.com, wanpengli@...cent.com,
x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3 02/32] x86/coco: Add API to handle encryption mask
On Tue, Feb 22, 2022 at 01:28:56AM +0300, Kirill A. Shutemov wrote:
> On Mon, Feb 21, 2022 at 11:28:16AM -0800, Dave Hansen wrote:
> > I'm just a bit confused why *this* was chosen as the cc_whatever() hook.
> > Just like the mask function, it has one spot where it gets used:
> >
> > +#define pgprot_encrypted(prot) __pgprot(cc_mkenc(pgprot_val(prot)))
> > +#define pgprot_decrypted(prot) __pgprot(cc_mkdec(pgprot_val(prot)))
> >
> > So, why bother having another level of abstraction?
> >
> > Why don't we just have:
> >
> > pgprot_t cc_mkenc(pgprot prot)
> > pgprot_t cc_mkenc(pgprot prot)
> >
> > and *no* pgprot_{en,de}crypted()?
>
> Okay. Let me try this.
Below it how it would look like.
I don't like it, especially, tdx_enc_status_changed() case. There are more
cases like this in attestation code.
I would rather make cc_mkenc()/cc_mkdec() to operate on u64 (or
phys_addr_t?) while pgprot_encrypted()/pgprot_decrypted() cover pgprot_t.
It also makes set_memory cleaner:
cpa.mask_set = __pgprot(enc ? cc_mkenc(0) : cc_mkdec(0));
cpa.mask_clr = __pgprot(enc ? cc_mkdec(0) : cc_mkenc(0));
Opinions?
diff --git a/arch/x86/coco/tdx.c b/arch/x86/coco/tdx.c
index fb32c271fe34..bf5ba7d5b736 100644
--- a/arch/x86/coco/tdx.c
+++ b/arch/x86/coco/tdx.c
@@ -514,8 +514,8 @@ static int tdx_enc_status_changed(unsigned long vaddr, int numpages, bool enc)
return -EINVAL;
if (!enc) {
- start = cc_mkenc(start);
- end = cc_mkenc(end);
+ start |= pgprot_val(cc_mkenc(__pgprot(0)));
+ end |= pgprot_val(cc_mkenc(__pgprot(0)));
}
/*
diff --git a/arch/x86/include/asm/coco.h b/arch/x86/include/asm/coco.h
index 802d87d08e31..fba1dd2ef319 100644
--- a/arch/x86/include/asm/coco.h
+++ b/arch/x86/include/asm/coco.h
@@ -14,13 +14,18 @@ enum cc_vendor {
void cc_init(enum cc_vendor, u64 mask);
#ifdef CONFIG_ARCH_HAS_CC_PLATFORM
-u64 cc_get_mask(bool enc);
-u64 cc_mkenc(u64 val);
-u64 cc_mkdec(u64 val);
+pgprot_t cc_mkenc(pgprot_t prot);
+pgprot_t cc_mkdec(pgprot_t prot);
#else
-#define cc_get_mask(enc) 0
-#define cc_mkenc(val) (val)
-#define cc_mkdec(val) (val)
+static inline pgprot_t cc_mkenc(pgprot_t prot)
+{
+ return prot;
+}
+
+static inline pgprot_t cc_mkdec(pgprot_t prot)
+{
+ return prot;
+}
#endif
#endif /* _ASM_X86_COCO_H */
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 62ab07e24aef..8cba0d258e49 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -36,8 +36,8 @@ void ptdump_walk_user_pgd_level_checkwx(void);
/*
* Macros to add or remove encryption attribute
*/
-#define pgprot_encrypted(prot) __pgprot(cc_mkenc(pgprot_val(prot)))
-#define pgprot_decrypted(prot) __pgprot(cc_mkdec(pgprot_val(prot)))
+#define pgprot_encrypted(prot) cc_mkenc(prot)
+#define pgprot_decrypted(prot) cc_mkdec(prot)
#ifdef CONFIG_DEBUG_WX
#define debug_checkwx() ptdump_walk_pgd_level_checkwx()
diff --git a/arch/x86/kernel/cc_platform.c b/arch/x86/kernel/cc_platform.c
index 12a34e80ef50..d13a034e9a21 100644
--- a/arch/x86/kernel/cc_platform.c
+++ b/arch/x86/kernel/cc_platform.c
@@ -12,6 +12,7 @@
#include <asm/coco.h>
#include <asm/processor.h>
+#include <asm/pgtable_types.h>
static u64 cc_mask;
static enum cc_vendor cc_vendor;
@@ -93,39 +94,27 @@ bool cc_platform_has(enum cc_attr attr)
}
EXPORT_SYMBOL_GPL(cc_platform_has);
-u64 cc_get_mask(bool enc)
+pgprot_t cc_mkenc(pgprot_t prot)
{
switch (cc_vendor) {
case CC_VENDOR_AMD:
- return enc ? cc_mask : 0;
+ return __pgprot(pgprot_val(prot) | cc_mask);
case CC_VENDOR_INTEL:
- return enc ? 0 : cc_mask;
+ return __pgprot(pgprot_val(prot) & ~cc_mask);
default:
- return 0;
+ return prot;
}
}
-u64 cc_mkenc(u64 val)
+pgprot_t cc_mkdec(pgprot_t prot)
{
switch (cc_vendor) {
case CC_VENDOR_AMD:
- return val | cc_mask;
+ return __pgprot(pgprot_val(prot) & ~cc_mask);
case CC_VENDOR_INTEL:
- return val & ~cc_mask;
+ return __pgprot(pgprot_val(prot) | cc_mask);
default:
- return val;
- }
-}
-
-u64 cc_mkdec(u64 val)
-{
- switch (cc_vendor) {
- case CC_VENDOR_AMD:
- return val & ~cc_mask;
- case CC_VENDOR_INTEL:
- return val | cc_mask;
- default:
- return val;
+ return prot;
}
}
EXPORT_SYMBOL_GPL(cc_mkdec);
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 65a27dec095f..1ef63ea377dd 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -1999,8 +1999,8 @@ static int __set_memory_enc_pgtable(unsigned long addr, int numpages, bool enc)
memset(&cpa, 0, sizeof(cpa));
cpa.vaddr = &addr;
cpa.numpages = numpages;
- cpa.mask_set = __pgprot(cc_get_mask(enc));
- cpa.mask_clr = __pgprot(cc_get_mask(!enc));
+ cpa.mask_set = enc ? cc_mkenc(__pgprot(0)) : cc_mkdec(__pgprot(0));
+ cpa.mask_clr = enc ? cc_mkdec(__pgprot(0)) : cc_mkenc(__pgprot(0));
cpa.pgd = init_mm.pgd;
/* Must avoid aliasing mappings in the highmem code */
--
Kirill A. Shutemov
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