Re: [PATCH v2 32/58] i386/tdx: Track RAM entries for TDX VM

[Daniel P . Berrangé]

On Fri, Aug 18, 2023 at 05:50:15AM -0400, Xiaoyao Li wrote:
> The RAM of TDX VM can be classified into two types:
> 
>  - TDX_RAM_UNACCEPTED: default type of TDX memory, which needs to be
>    accepted by TDX guest before it can be used and will be all-zeros
>    after being accepted.
> 
>  - TDX_RAM_ADDED: the RAM that is ADD'ed to TD guest before running, and
>    can be used directly. E.g., TD HOB and TEMP MEM that needed by TDVF.
> 
> Maintain TdxRamEntries[] which grabs the initial RAM info from e820 table
> and mark each RAM range as default type TDX_RAM_UNACCEPTED.
> 
> Then turn the range of TD HOB and TEMP MEM to TDX_RAM_ADDED since these
> ranges will be ADD'ed before TD runs and no need to be accepted runtime.
> 
> The TdxRamEntries[] are later used to setup the memory TD resource HOB
> that passes memory info from QEMU to TDVF.
> 
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> Acked-by: Gerd Hoffmann <kraxel@redhat.com>
> 
> ---
> Changes from RFC v4:
>   - simplify the algorithm of tdx_accept_ram_range() (Suggested-by: Gerd 
> Hoffman)
>     (1) Change the existing entry to cover the accepted ram range.
>     (2) If there is room before the accepted ram range add a
>       TDX_RAM_UNACCEPTED entry for that.
>     (3) If there is room after the accepted ram range add a
>       TDX_RAM_UNACCEPTED entry for that.
> ---
>  target/i386/kvm/tdx.c | 110 ++++++++++++++++++++++++++++++++++++++++++
>  target/i386/kvm/tdx.h |  14 ++++++
>  2 files changed, 124 insertions(+)
> 
> diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
> index bb806736b4ff..ed617ebab266 100644
> --- a/target/i386/kvm/tdx.c
> +++ b/target/i386/kvm/tdx.c
> +static int tdx_accept_ram_range(uint64_t address, uint64_t length)
> +{
> +    uint64_t head_start, tail_start, head_length, tail_length;
> +    uint64_t tmp_address, tmp_length;
> +    TdxRamEntry *e;
> +    int i;
> +
> +    for (i = 0; i < tdx_guest->nr_ram_entries; i++) {
> +        e = &tdx_guest->ram_entries[i];
> +
> +        if (address + length <= e->address ||
> +            e->address + e->length <= address) {
> +                continue;

Indented too far

> +        }
> +
> +        /*
> +         * The to-be-accepted ram range must be fully contained by one
> +         * RAM entry.
> +         */
> +        if (e->address > address ||
> +            e->address + e->length < address + length) {
> +            return -EINVAL;
> +        }
> +
> +        if (e->type == TDX_RAM_ADDED) {
> +            return -EINVAL;
> +        }
> +
> +        break;
> +    }
> +
> +    if (i == tdx_guest->nr_ram_entries) {
> +        return -1;
> +    }
> +
> +    tmp_address = e->address;
> +    tmp_length = e->length;
> +
> +    e->address = address;
> +    e->length = length;
> +    e->type = TDX_RAM_ADDED;
> +
> +    head_length = address - tmp_address;
> +    if (head_length > 0) {
> +        head_start = tmp_address;
> +        tdx_add_ram_entry(head_start, head_length, TDX_RAM_UNACCEPTED);
> +    }
> +
> +    tail_start = address + length;
> +    if (tail_start < tmp_address + tmp_length) {
> +        tail_length = tmp_address + tmp_length - tail_start;
> +        tdx_add_ram_entry(tail_start, tail_length, TDX_RAM_UNACCEPTED);
> +    }
> +
> +    return 0;
> +}

With regards,
Daniel
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