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Tue, 26 Mar 2024 06:40:08 -0700 (PDT) Message-ID: Date: Tue, 26 Mar 2024 14:40:06 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 5/5] x86/PVH: Support relocatable dom0 kernels Content-Language: en-US To: Jason Andryuk Cc: Andrew Cooper , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , George Dunlap , Julien Grall , Stefano Stabellini , xen-devel@lists.xenproject.org References: <20240325204515.250203-1-jason.andryuk@amd.com> <20240325204515.250203-6-jason.andryuk@amd.com> <770d3292-34cf-4e21-acb6-bd1f9caf5fef@suse.com> 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 26.03.2024 14:24, Jason Andryuk wrote: > On 2024-03-26 03:50, Jan Beulich wrote: >> On 25.03.2024 21:45, Jason Andryuk wrote: >>> @@ -227,6 +239,27 @@ elf_errorstatus elf_xen_parse_note(struct elf_binary *elf, >>> case XEN_ELFNOTE_PHYS32_ENTRY: >>> parms->phys_entry = val; >>> break; >>> + >>> + case XEN_ELFNOTE_PHYS32_RELOC: >>> + parms->phys_reloc = true; >>> + >>> + if ( descsz >= 4 ) >>> + { >>> + parms->phys_max = elf_note_numeric_array(elf, note, 4, 0); >>> + elf_msg(elf, " = max: %#"PRIx32, parms->phys_max); >> >> As indicated before, I consider the = here a little odd. > > I retained = for consistency with other notes: > ELF: note: PHYS32_RELOC = max: 0x40000000 min: 0x1000000 align: 0x200000 > ELF: note: PHYS32_ENTRY = 0x1000000 > ELF: note: GUEST_OS = "linux" > > I guess whitespace and labels makes it clear, so I'll drop the '='. > >>> + } >>> + if ( descsz >= 8 ) >>> + { >>> + parms->phys_min = elf_note_numeric_array(elf, note, 4, 1); >>> + elf_msg(elf, " min: %#"PRIx32, parms->phys_min); >>> + } >>> + if ( descsz >= 12 ) >>> + { >>> + parms->phys_align = elf_note_numeric_array(elf, note, 4, 2); >>> + elf_msg(elf, " align: %#"PRIx32, parms->phys_align); >>> + } >> >> I'd like us to reconsider this ordering: I'm inclined to say that MAX isn't >> the most likely one a guest may find a need to use. Instead I'd expect both >> MIN and ALIGN wanting to be given higher priority; what I'm less certain >> about is the ordering between the two. To keep MIN and MAX adjacent, how >> about ALIGN, MIN, MAX? > > ALIGN, MIN, MAX works for me. > > On the Linux side, I'm expecting them all to be set: > ALIGN = CONFIG_PHYSICAL_ALIGN > MIN = LOAD_PHYSICAL_ADDR > MAX = KERNEL_IMAGE_SIZE > > You need enough identity page tables to cover up to MAX. > LOAD_PHYSICAL_ADDR is used as a minimum, so requesting placement above > MIN makes sense to me. Hmm, setting MIN like this means moving down is precluded. Why would it not be possible to move a kernel to lower than the default of 16M, when CONFIG_PHYSICAL_START can be as low as 0? (In fact, I doubt 0 would work if chosen, but 2M surely does work, as I build some of my Dom0 kernels that way.) MAX, otoh, I guess really wants setting as you say, for KERNEL_IMAGE_SIZE actually being commented upon as mis-named. Just that it now really wants to be KERNEL_IMAGE_SIZE-1. Jan