linux-kernel - Re: [PATCH v3 5/6] fs/core/vmcore: Move sev

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Message-ID: <c85ae8ff-3b7b-88bf-6b6a-c41b159c9cc2@redhat.com>
Date:   Fri, 19 Jul 2019 12:59:41 +0800
From:   lijiang <lijiang@...hat.com>
To:     "Lendacky, Thomas" <Thomas.Lendacky@....com>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        "x86@...nel.org" <x86@...nel.org>
Cc:     "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Halil Pasic <pasic@...ux.ibm.com>,
        Mike Anderson <andmike@...ux.ibm.com>,
        Ram Pai <linuxram@...ibm.com>, Baoquan He <bhe@...hat.com>
Subject: Re: [PATCH v3 5/6] fs/core/vmcore: Move sev_active() reference to x86
 arch code

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@...ux.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@...hat.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 */
>>  
>>