From: Brijesh Singh <brijesh.singh@amd.com>
To: Arnd Bergmann <arnd@arndb.de>, David Laight <David.Laight@aculab.com>
Cc: brijesh.singh@amd.com,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"x86@kernel.org" <x86@kernel.org>,
"linux-efi@vger.kernel.org" <linux-efi@vger.kernel.org>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"Fenghua Yu" <fenghua.yu@intel.com>,
"Matt Fleming" <matt@codeblueprint.co.uk>,
"David Howells" <dhowells@redhat.com>,
"Paul Mackerras" <paulus@samba.org>,
"H . Peter Anvin" <hpa@zytor.com>,
"Christoph Lameter" <cl@linux.com>,
"Jonathan Corbet" <corbet@lwn.net>,
"Radim Krcmár" <rkrcmar@redhat.com>,
"Piotr Luc" <piotr.luc@intel.com>,
"Ingo Molnar" <mingo@redhat.com>,
"Dave Airlie" <airlied@redhat.com>,
"Borislav Petkov" <bp@suse.de>,
"Tom Lendacky" <thomas.lendacky@amd.com>,
"Kees Cook" <keescook@chromium.org>,
"Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com>,
"Reza Arbab" <arbab@linux.vnet.ibm.com>,
"Andy Lutomirski" <luto@kernel.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Laura Abbott" <labbott@redhat.com>,
"Tony Luck" <tony.luck@intel.com>,
"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
"Eric Biederman" <ebiederm@xmission.com>,
"Tejun Heo" <tj@kernel.org>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
"Lu Baolu" <baolu.lu@linux.intel.com>
Subject: Re: [RFC Part1 PATCH v3 13/17] x86/io: Unroll string I/O when SEV is active
Date: Wed, 26 Jul 2017 14:24:45 -0500 [thread overview]
Message-ID: <ed6d4ce7-97a6-f664-d7d7-4ff48bc6f06a@amd.com> (raw)
In-Reply-To: <CAK8P3a3h7JpmkW7W=HwqAuWWmro=ngj6HSeiiML_=T82x-FtZQ@mail.gmail.com>
Hi Arnd and David,
On 07/26/2017 05:45 AM, Arnd Bergmann wrote:
> On Tue, Jul 25, 2017 at 11:51 AM, David Laight <David.Laight@aculab.com> wrote:
>> From: Brijesh Singh
>>> Sent: 24 July 2017 20:08
>>> From: Tom Lendacky <thomas.lendacky@amd.com>
>>>
>>> Secure Encrypted Virtualization (SEV) does not support string I/O, so
>>> unroll the string I/O operation into a loop operating on one element at
>>> a time.
>>>
>>> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
>>> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
>>> ---
>>> arch/x86/include/asm/io.h | 26 ++++++++++++++++++++++----
>>> 1 file changed, 22 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
>>> index e080a39..2f3c002 100644
>>> --- a/arch/x86/include/asm/io.h
>>> +++ b/arch/x86/include/asm/io.h
>>> @@ -327,14 +327,32 @@ static inline unsigned type in##bwl##_p(int port) \
>>> \
>>> static inline void outs##bwl(int port, const void *addr, unsigned long count) \
>>> {
>
> This will clash with a fix I did to add a "memory" clobber
> for the traditional implementation, see
> https://patchwork.kernel.org/patch/9854573/
>
>> Is it even worth leaving these as inline functions?
>> Given the speed of IO cycles it is unlikely that the cost of calling a real
>> function will be significant.
>> The code bloat reduction will be significant.
>
> I think the smallest code would be the original "rep insb" etc, which
> should be smaller than a function call, unlike the loop. Then again,
> there is a rather small number of affected device drivers, almost all
> of them for ancient hardware that you won't even build in a 64-bit
> x86 kernel, see the list below. The only user I found that is actually
> still relevant is drivers/tty/hvc/hvc_xen.c, which uses it for the early
> console.
There are some indirect user of string I/O functions. The following functions
defined in lib/iomap.c calls rep version of ins and outs.
- ioread8_rep, ioread16_rep, ioread32_rep
- iowrite8_rep, iowrite16_rep, iowrite32_rep
I found that several drivers use above functions.
Here is one approach to convert it into non-inline functions. In this approach,
I have added a new file arch/x86/kernel/io.c which provides non rep version of
string I/O routines. The file gets built and used only when AMD_MEM_ENCRYPT is
enabled. On positive side, if we don't build kernel with AMD_MEM_ENCRYPT support
then we use inline routines, when AMD_MEM_ENCRYPT is built then we make a function
call. Inside the function we unroll only when SEV is active.
Do you see any issue with this approach ? thanks
diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index e080a39..104927d 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -323,8 +323,9 @@ static inline unsigned type in##bwl##_p(int port) \
unsigned type value = in##bwl(port); \
slow_down_io(); \
return value; \
-} \
- \
+}
+
+#define BUILDIO_REP(bwl, bw, type) \
static inline void outs##bwl(int port, const void *addr, unsigned long count) \
{ \
asm volatile("rep; outs" #bwl \
@@ -335,12 +336,31 @@ static inline void ins##bwl(int port, void *addr, unsigned long count) \
{ \
asm volatile("rep; ins" #bwl \
: "+D"(addr), "+c"(count) : "d"(port)); \
-}
+} \
BUILDIO(b, b, char)
BUILDIO(w, w, short)
BUILDIO(l, , int)
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+extern void outsb_try_rep(int port, const void *addr, unsigned long count);
+extern void insb_try_rep(int port, void *addr, unsigned long count);
+extern void outsw_try_rep(int port, const void *addr, unsigned long count);
+extern void insw_try_rep(int port, void *addr, unsigned long count);
+extern void outsl_try_rep(int port, const void *addr, unsigned long count);
+extern void insl_try_rep(int port, void *addr, unsigned long count);
+#define outsb outsb_try_rep
+#define insb insb_try_rep
+#define outsw outsw_try_rep
+#define insw insw_try_rep
+#define outsl outsl_try_rep
+#define insl insl_try_rep
+#else
+BUILDIO_REP(b, b, char)
+BUILDIO_REP(w, w, short)
+BUILDIO_REP(l, , int)
+#endif
+
extern void *xlate_dev_mem_ptr(phys_addr_t phys);
extern void unxlate_dev_mem_ptr(phys_addr_t phys, void *addr);
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index a01892b..3b6e2a3 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -42,6 +42,7 @@ CFLAGS_irq.o := -I$(src)/../include/asm/trace
obj-y := process_$(BITS).o signal.o
obj-$(CONFIG_COMPAT) += signal_compat.o
+obj-$(CONFIG_AMD_MEM_ENCRYPT) += io.o
obj-y += traps.o irq.o irq_$(BITS).o dumpstack_$(BITS).o
obj-y += time.o ioport.o dumpstack.o nmi.o
obj-$(CONFIG_MODIFY_LDT_SYSCALL) += ldt.o
diff --git a/arch/x86/kernel/io.c b/arch/x86/kernel/io.c
new file mode 100644
index 0000000..f58afa9
--- /dev/null
+++ b/arch/x86/kernel/io.c
@@ -0,0 +1,87 @@
+#include <linux/types.h>
+#include <linux/io.h>
+#include <asm/io.h>
+
+void outsb_try_rep(int port, const void *addr, unsigned long count)
+{
+ if (sev_active()) {
+ unsigned char *value = (unsigned char *)addr;
+ while (count) {
+ outb(*value, port);
+ value++;
+ count--;
+ }
+ } else {
+ asm volatile("rep; outsb" : "+S"(addr), "+c"(count) : "d"(port));
+ }
+}
+
+void insb_try_rep(int port, void *addr, unsigned long count)
+{
+ if (sev_active()) {
+ unsigned char *value = (unsigned char *)addr;
+ while (count) {
+ *value = inb(port);
+ value++;
+ count--;
+ }
+ } else {
+ asm volatile("rep; insb" : "+D"(addr), "+c"(count) : "d"(port));
+ }
+}
+
+void outsw_try_rep(int port, const void *addr, unsigned long count)
+{
+ if (sev_active()) {
+ unsigned short *value = (unsigned short *)addr;
+ while (count) {
+ outw(*value, port);
+ value++;
+ count--;
+ }
+ } else {
+ asm volatile("rep; outsw" : "+S"(addr), "+c"(count) : "d"(port));
+ }
+}
+void insw_try_rep(int port, void *addr, unsigned long count)
+{
+ if (sev_active()) {
+ unsigned short *value = (unsigned short *)addr;
+ while (count) {
+ *value = inw(port);
+ value++;
+ count--;
+ }
+ } else {
+ asm volatile("rep; insw" : "+D"(addr), "+c"(count) : "d"(port));
+ }
+}
+
+void outsl_try_rep(int port, const void *addr, unsigned long count)
+{
+ if (sev_active()) {
+ unsigned int *value = (unsigned int *)addr;
+ while (count) {
+ outl(*value, port);
+ value++;
+ count--;
+ }
+ } else {
+ asm volatile("rep; outsl" : "+S"(addr), "+c"(count) : "d"(port));
+ }
+}
+
+void insl_try_rep(int port, void *addr, unsigned long count)
+{
+ if (sev_active()) {
+ unsigned int *value = (unsigned int *)addr;
+ while (count) {
+ *value = inl(port);
+ value++;
+ count--;
+ }
+ } else {
+ asm volatile("rep; insl" : "+D"(addr), "+c"(count) : "d"(port));
+ }
+}
next prev parent reply other threads:[~2017-07-26 19:24 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-24 19:07 [RFC Part1 PATCH v3 00/17] x86: Secure Encrypted Virtualization (AMD) Brijesh Singh
2017-07-24 19:07 ` [RFC Part1 PATCH v3 01/17] Documentation/x86: Add AMD Secure Encrypted Virtualization (SEV) descrption Brijesh Singh
2017-07-25 5:45 ` Borislav Petkov
2017-07-25 14:59 ` Brijesh Singh
2017-07-24 19:07 ` [RFC Part1 PATCH v3 02/17] x86/CPU/AMD: Add the Secure Encrypted Virtualization CPU feature Brijesh Singh
2017-07-25 10:26 ` Borislav Petkov
2017-07-25 14:29 ` Tom Lendacky
2017-07-25 14:36 ` Borislav Petkov
2017-07-25 14:58 ` Tom Lendacky
2017-07-25 15:13 ` Borislav Petkov
2017-07-25 15:29 ` Tom Lendacky
2017-07-25 15:33 ` Borislav Petkov
2017-08-09 18:17 ` Tom Lendacky
2017-08-17 8:12 ` Borislav Petkov
2017-07-24 19:07 ` [RFC Part1 PATCH v3 03/17] x86/mm: Secure Encrypted Virtualization (SEV) support Brijesh Singh
2017-07-26 4:28 ` Borislav Petkov
2017-07-26 16:47 ` Tom Lendacky
2017-07-27 13:39 ` Borislav Petkov
2017-07-24 19:07 ` [RFC Part1 PATCH v3 04/17] x86/mm: Don't attempt to encrypt initrd under SEV Brijesh Singh
2017-07-26 14:44 ` Borislav Petkov
2017-07-24 19:07 ` [RFC Part1 PATCH v3 05/17] x86, realmode: Don't decrypt trampoline area " Brijesh Singh
2017-07-26 16:03 ` Borislav Petkov
2017-08-10 13:03 ` Tom Lendacky
2017-07-24 19:07 ` [RFC Part1 PATCH v3 06/17] x86/mm: Use encrypted access of boot related data with SEV Brijesh Singh
2017-07-27 13:31 ` Borislav Petkov
2017-08-17 18:05 ` Tom Lendacky
2017-07-24 19:07 ` [RFC Part1 PATCH v3 07/17] x86/mm: Include SEV for encryption memory attribute changes Brijesh Singh
2017-07-27 14:58 ` Borislav Petkov
2017-07-28 8:47 ` David Laight
2017-08-17 18:21 ` Tom Lendacky
2017-08-17 18:10 ` Tom Lendacky
2017-07-24 19:07 ` [RFC Part1 PATCH v3 08/17] x86/efi: Access EFI data as encrypted when SEV is active Brijesh Singh
2017-07-28 10:31 ` Borislav Petkov
2017-08-17 18:42 ` Tom Lendacky
2017-07-24 19:07 ` [RFC Part1 PATCH v3 09/17] resource: Consolidate resource walking code Brijesh Singh
2017-07-28 15:23 ` Borislav Petkov
2017-08-17 18:55 ` Tom Lendacky
2017-08-17 19:03 ` Tom Lendacky
2017-07-24 19:07 ` [RFC Part1 PATCH v3 10/17] resource: Provide resource struct in resource walk callback Brijesh Singh
2017-07-31 8:26 ` Borislav Petkov
2017-07-31 22:19 ` Kees Cook
2017-07-24 19:07 ` [RFC Part1 PATCH v3 11/17] x86/mm, resource: Use PAGE_KERNEL protection for ioremap of memory pages Brijesh Singh
2017-08-02 4:02 ` Borislav Petkov
2017-08-17 19:22 ` Tom Lendacky
2017-07-24 19:07 ` [RFC Part1 PATCH v3 12/17] x86/mm: DMA support for SEV memory encryption Brijesh Singh
2017-08-07 3:48 ` Borislav Petkov
2017-08-17 19:35 ` Tom Lendacky
2017-07-24 19:07 ` [RFC Part1 PATCH v3 13/17] x86/io: Unroll string I/O when SEV is active Brijesh Singh
2017-07-25 9:51 ` David Laight
2017-07-26 10:45 ` Arnd Bergmann
2017-07-26 19:24 ` Brijesh Singh [this message]
2017-07-26 19:26 ` H. Peter Anvin
2017-07-26 20:07 ` Brijesh Singh
2017-07-27 7:45 ` David Laight
2017-08-22 16:52 ` Borislav Petkov
2017-09-15 12:24 ` Borislav Petkov
2017-09-15 14:13 ` Brijesh Singh
2017-09-15 14:40 ` Borislav Petkov
2017-09-15 14:48 ` Brijesh Singh
2017-09-15 16:22 ` Borislav Petkov
2017-09-15 16:27 ` Brijesh Singh
2017-07-24 19:07 ` [RFC Part1 PATCH v3 14/17] x86/boot: Add early boot support when running with SEV active Brijesh Singh
2017-08-23 15:30 ` Borislav Petkov
2017-08-24 18:54 ` Tom Lendacky
2017-08-25 12:54 ` Borislav Petkov
2017-07-24 19:07 ` [RFC Part1 PATCH v3 15/17] x86: Add support for changing memory encryption attribute in early boot Brijesh Singh
2017-08-28 10:51 ` Borislav Petkov
2017-08-28 11:49 ` Brijesh Singh
2017-07-24 19:07 ` [RFC Part1 PATCH v3 16/17] X86/KVM: Provide support to create Guest and HV shared per-CPU variables Brijesh Singh
2017-08-29 10:22 ` Borislav Petkov
2017-08-30 16:18 ` Brijesh Singh
2017-08-30 17:46 ` Borislav Petkov
2017-09-01 22:52 ` Brijesh Singh
2017-09-02 3:21 ` Andy Lutomirski
2017-09-03 2:34 ` Brijesh Singh
2017-09-04 17:05 ` Borislav Petkov
2017-09-04 17:47 ` Brijesh Singh
2017-07-24 19:07 ` [RFC Part1 PATCH v3 17/17] X86/KVM: Clear encryption attribute when SEV is active Brijesh Singh
2017-08-31 15:06 ` Borislav Petkov
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