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Tue, 05 Aug 2025 05:38:39 -0700 (PDT) Message-ID: <31691bf7-94bf-4f73-b04c-a32f86bb0e37@suse.com> Date: Tue, 5 Aug 2025 14:38:38 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 8/8] x86/mm: adjust loop in arch_init_memory() to iterate over the PDX space To: Roger Pau Monne Cc: Andrew Cooper , xen-devel@lists.xenproject.org References: <20250805095257.74975-1-roger.pau@citrix.com> <20250805095257.74975-9-roger.pau@citrix.com> Content-Language: en-US From: Jan Beulich Autocrypt: addr=jbeulich@suse.com; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL In-Reply-To: <20250805095257.74975-9-roger.pau@citrix.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 05.08.2025 11:52, Roger Pau Monne wrote: > --- a/xen/arch/x86/mm.c > +++ b/xen/arch/x86/mm.c > @@ -275,7 +275,7 @@ static void __init assign_io_page(struct page_info *page) > > void __init arch_init_memory(void) > { > - unsigned long i, pfn, rstart_pfn, rend_pfn, iostart_pfn, ioend_pfn; > + unsigned long i, pfn, rstart_pfn, rend_pfn, iostart_pfn, ioend_pfn, pdx; > > /* > * Basic guest-accessible flags: > @@ -328,9 +328,20 @@ void __init arch_init_memory(void) > destroy_xen_mappings((unsigned long)mfn_to_virt(iostart_pfn), > (unsigned long)mfn_to_virt(ioend_pfn)); > > - /* Mark as I/O up to next RAM region. */ > - for ( ; pfn < rstart_pfn; pfn++ ) > + /* > + * Mark as I/O up to next RAM region. Iterate over the PDX space to > + * skip holes which would always fail the mfn_valid() check. > + * > + * pfn_to_pdx() requires a valid (iow: RAM) PFN to convert to PDX, > + * hence provide pfn - 1, which is the tailing PFN from the last RAM > + * range, or pdx 0 if the input pfn is 0. > + */ > + for ( pdx = pfn ? pfn_to_pdx(pfn - 1) + 1 : 0; > + pdx < pfn_to_pdx(rstart_pfn); > + pdx++ ) > { > + pfn = pdx_to_pfn(pdx); > + > if ( !mfn_valid(_mfn(pfn)) ) > continue; > As much as I would have liked to ack this, I fear there's another caveat here: At the top of the loop we check not only for RAM, but also for UNUSABLE. The latter, like RAM, shouldn't be marked I/O, but we also can't use PFN <-> PDX transformations on any such page. Jan