Re: [PATCH 1/4 v8] x86/ioremap: add a function ioremap_encrypted() to remap kdump old memory

Baoquan He
2018-09-27T02:06:55Z

Hi Lianbo,

On 09/26/18 at 05:34pm, lijiang wrote:
> When SME is enabled on AMD machine, the memory is encrypted in the first
> kernel. In this case, SME also needs to be enabled in kdump kernel, and
> we have to remap the old memory with the memory encryption mask.
>
> Here we only talk about the case that SME is active in the first kernel,
> and only care it's active too in kdump kernel. there are four cases we
> need considered.
>
> a. dump vmcore
> It is encrypted in the first kernel, and needs be read out in kdump
> kernel.
>
> b. crash notes
> When dumping vmcore, the people usually need to read the useful
> information from notes, and the notes is also encrypted.
>
> c. iommu device table
> It is allocated by kernel, need fill its pointer into mmio of amd iommu.
> It's encrypted in the first kernel, need read the old content to analyze
> and get useful information.
>
> d. mmio of amd iommu
> Register reported by amd firmware, it's not RAM, we don't encrypt in
> both the first kernel and kdump kernel.
>
> To achieve the goal, the solution is:
> 1. add a new bool parameter "encrypted" to __ioremap_caller()
> It is a low level function, and check the newly added parameter, if it's
> true and in kdump kernel, will remap the memory with sme mask.
>
> 2. add a new function ioremap_encrypted() to explicitly passed in a "true"
> value for "encrypted".
> For above a, b, c, we will call ioremap_encrypted();
>
> 3. adjust all existed ioremap wrapper functions, passed in "false" for
> encrypted to make them an before.
>
> ioremap_encrypted()\
> ioremap_cache() |
> ioremap_prot() |
> ioremap_wt() |->__ioremap_caller()
> ioremap_wc() |
> ioremap_uc() |
> ioremap_nocache() /

Thanks, I think it's better. Since no code change, just patch log
improvement, maybe you can repost a series and carry both Tom and
Joerg's ACK.