Re: [PATCH v3 5/6] fs/core/vmcore: Move sev_active() reference to x86 arch code

lijiang
2019-07-19T05:00:13Z

在 2019年07月19日 01:47, Lendacky, Thomas 写道:
> On 7/17/19 10:28 PM, Thiago Jung Bauermann wrote:
>> Secure Encrypted Virtualization is an x86-specific feature, so it shouldn't
>> appear in generic kernel code because it forces non-x86 architectures to
>> define the sev_active() function, which doesn't make a lot of sense.
>>
>> To solve this problem, add an x86 elfcorehdr_read() function to override
>> the generic weak implementation. To do that, it's necessary to make
>> read_from_oldmem() public so that it can be used outside of vmcore.c.
>>
>> Also, remove the export for sev_active() since it's only used in files that
>> won't be built as modules.
>>
>> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
>
> Adding Lianbo and Baoquan, who recently worked on this, for their review.
>

This change looks good to me.

Reviewed-by: Lianbo Jiang <lijiang@redhat.com>

Thanks.
Lianbo

> Thanks,
> Tom
>
>> ---
>> arch/x86/kernel/crash_dump_64.c | 5 +++++
>> arch/x86/mm/mem_encrypt.c | 1 -
>> fs/proc/vmcore.c | 8 ++++----
>> include/linux/crash_dump.h | 14 ++++++++++++++
>> include/linux/mem_encrypt.h | 1 -
>> 5 files changed, 23 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/x86/kernel/crash_dump_64.c b/arch/x86/kernel/crash_dump_64.c
>> index 22369dd5de3b..045e82e8945b 100644
>> --- a/arch/x86/kernel/crash_dump_64.c
>> +++ b/arch/x86/kernel/crash_dump_64.c
>> @@ -70,3 +70,8 @@ ssize_t copy_oldmem_page_encrypted(unsigned long pfn, char *buf, size_t csize,
>> {
>> return __copy_oldmem_page(pfn, buf, csize, offset, userbuf, true);
>> }
>> +
>> +ssize_t elfcorehdr_read(char *buf, size_t count, u64 *ppos)
>> +{
>> + return read_from_oldmem(buf, count, ppos, 0, sev_active());
>> +}
>> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
>> index 7139f2f43955..b1e823441093 100644
>> --- a/arch/x86/mm/mem_encrypt.c
>> +++ b/arch/x86/mm/mem_encrypt.c
>> @@ -349,7 +349,6 @@ bool sev_active(void)
>> {
>> return sme_me_mask && sev_enabled;
>> }
>> -EXPORT_SYMBOL(sev_active);
>>
>> /* Override for DMA direct allocation check - ARCH_HAS_FORCE_DMA_UNENCRYPTED */
>> bool force_dma_unencrypted(struct device *dev)
>> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
>> index 57957c91c6df..ca1f20bedd8c 100644
>> --- a/fs/proc/vmcore.c
>> +++ b/fs/proc/vmcore.c
>> @@ -100,9 +100,9 @@ static int pfn_is_ram(unsigned long pfn)
>> }
>>
>> /* Reads a page from the oldmem device from given offset. */
>> -static ssize_t read_from_oldmem(char *buf, size_t count,
>> - u64 *ppos, int userbuf,
>> - bool encrypted)
>> +ssize_t read_from_oldmem(char *buf, size_t count,
>> + u64 *ppos, int userbuf,
>> + bool encrypted)
>> {
>> unsigned long pfn, offset;
>> size_t nr_bytes;
>> @@ -166,7 +166,7 @@ void __weak elfcorehdr_free(unsigned long long addr)
>> */
>> ssize_t __weak elfcorehdr_read(char *buf, size_t count, u64 *ppos)
>> {
>> - return read_from_oldmem(buf, count, ppos, 0, sev_active());
>> + return read_from_oldmem(buf, count, ppos, 0, false);
>> }
>>
>> /*
>> diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h
>> index f774c5eb9e3c..4664fc1871de 100644
>> --- a/include/linux/crash_dump.h
>> +++ b/include/linux/crash_dump.h
>> @@ -115,4 +115,18 @@ static inline int vmcore_add_device_dump(struct vmcoredd_data *data)
>> return -EOPNOTSUPP;
>> }
>> #endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */
>> +
>> +#ifdef CONFIG_PROC_VMCORE
>> +ssize_t read_from_oldmem(char *buf, size_t count,
>> + u64 *ppos, int userbuf,
>> + bool encrypted);
>> +#else
>> +static inline ssize_t read_from_oldmem(char *buf, size_t count,
>> + u64 *ppos, int userbuf,
>> + bool encrypted)
>> +{
>> + return -EOPNOTSUPP;
>> +}
>> +#endif /* CONFIG_PROC_VMCORE */
>> +
>> #endif /* LINUX_CRASHDUMP_H */
>> diff --git a/include/linux/mem_encrypt.h b/include/linux/mem_encrypt.h
>> index 0c5b0ff9eb29..5c4a18a91f89 100644
>> --- a/include/linux/mem_encrypt.h
>> +++ b/include/linux/mem_encrypt.h
>> @@ -19,7 +19,6 @@
>> #else /* !CONFIG_ARCH_HAS_MEM_ENCRYPT */
>>
>> static inline bool mem_encrypt_active(void) { return false; }
>> -static inline bool sev_active(void) { return false; }
>>
>> #endif /* CONFIG_ARCH_HAS_MEM_ENCRYPT */
>>
>>